Administration Guide

Red Hat Ceph Storage 4

Administration of Red Hat Ceph Storage

Red Hat Ceph Storage Documentation Team

Abstract

This document describes how to manage processes, monitor cluster states, manage users, and add and remove daemons for Red Hat Ceph Storage.

Chapter 1. Ceph administration

A Red Hat Ceph Storage cluster is the foundation for all Ceph deployments. After deploying a Red Hat Ceph Storage cluster, there are administrative operations for keeping a Red Hat Ceph Storage cluster healthy and performing optimally.

The Red Hat Ceph Storage Administration Guide helps storage administrators to perform such tasks as:

  • How do I check the health of my Red Hat Ceph Storage cluster?
  • How do I start and stop the Red Hat Ceph Storage cluster services?
  • How do I add or remove an OSD from a running Red Hat Ceph Storage cluster?
  • How do I manage user authentication and access controls to the objects stored in a Red Hat Ceph Storage cluster?
  • I want to understand how to use overrides with a Red Hat Ceph Storage cluster.
  • I want to monitor the performance of the Red Hat Ceph Storage cluster.

A basic Ceph storage cluster consist of two types of daemons:

  • A Ceph Object Storage Device (OSD) stores data as objects within placement groups assigned to the OSD
  • A Ceph Monitor maintains a master copy of the cluster map

A production system will have three or more Ceph Monitors for high availability and typically a minimum of 50 OSDs for acceptable load balancing, data re-balancing and data recovery.

Chapter 2. Understanding process management for Ceph

As a storage administrator, you can manipulate the various Ceph daemons by type or instance, on bare-metal or in containers. Manipulating these daemons allows you to start, stop and restart all of the Ceph services as needed.

2.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

2.2. Ceph process management

In Red Hat Ceph Storage, all process management is done through the Systemd service. Each time you want to start, restart, and stop the Ceph daemons, you must specify the daemon type or the daemon instance.

Additional Resources

  • For more information about using Systemd, see the chapter Managing services with systemd in the Red Hat Enterprise Linux System Administrator’s Guide.

2.3. Starting, stopping, and restarting all Ceph daemons

Start, stop, and restart all Ceph daemons as an admin from the node.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Having root access to the node.

Procedure

  1. Starting all Ceph daemons:

    [root@admin ~]# systemctl start ceph.target
  2. Stopping all Ceph daemons:

    [root@admin ~]# systemctl stop ceph.target
  3. Restarting all Ceph daemons:

    [root@admin ~]# systemctl restart ceph.target

2.4. Starting, stopping, and restarting the Ceph daemons by type

To start, stop, or restart all Ceph daemons of a particular type, follow these procedures on the node running the Ceph daemons.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Having root access to the node.

Procedure

  • On Ceph Monitor nodes:

    Starting:

    [root@mon ~]# systemctl start ceph-mon.target

    Stopping:

    [root@mon ~]# systemctl stop ceph-mon.target

    Restarting:

    [root@mon ~]# systemctl restart ceph-mon.target

  • On Ceph Manager nodes:

    Starting:

    [root@mgr ~]# systemctl start ceph-mgr.target

    Stopping:

    [root@mgr ~]# systemctl stop ceph-mgr.target

    Restarting:

    [root@mgr ~]# systemctl restart ceph-mgr.target

  • On Ceph OSD nodes:

    Starting:

    [root@osd ~]# systemctl start ceph-osd.target

    Stopping:

    [root@osd ~]# systemctl stop ceph-osd.target

    Restarting:

    [root@osd ~]# systemctl restart ceph-osd.target

  • On Ceph Object Gateway nodes:

    Starting:

    [root@rgw ~]# systemctl start ceph-radosgw.target

    Stopping:

    [root@rgw ~]# systemctl stop ceph-radosgw.target

    Restarting:

    [root@rgw ~]# systemctl restart ceph-radosgw.target

2.5. Starting, stopping, and restarting the Ceph daemons by instance

To start, stop, or restart a Ceph daemon by instance, follow these procedures on the node running the Ceph daemons.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Having root access to the node.

Procedure

  • On a Ceph Monitor node:

    Starting:

    [root@mon ~]# systemctl start ceph-mon@MONITOR_HOST_NAME

    Stopping:

    [root@mon ~]# systemctl stop ceph-mon@MONITOR_HOST_NAME

    Restarting:

    [root@mon ~]# systemctl restart ceph-mon@MONITOR_HOST_NAME

    Replace

    • MONITOR_HOST_NAME with the name of the Ceph Monitor node.
  • On a Ceph Manager node:

    Starting:

    [root@mgr ~]# systemctl start ceph-mgr@MANAGER_HOST_NAME

    Stopping:

    [root@mgr ~]# systemctl stop ceph-mgr@MANAGER_HOST_NAME

    Restarting:

    [root@mgr ~]# systemctl restart ceph-mgr@MANAGER_HOST_NAME

    Replace

    • MANAGER_HOST_NAME with the name of the Ceph Manager node.
  • On a Ceph OSD node:

    Starting:

    [root@osd ~]# systemctl start ceph-osd@OSD_NUMBER

    Stopping:

    [root@osd ~]# systemctl stop ceph-osd@OSD_NUMBER

    Restarting:

    [root@osd ~]# systemctl restart ceph-osd@OSD_NUMBER

    Replace

    • OSD_NUMBER with the ID number of the Ceph OSD.

      For example, when looking at the ceph osd tree command output, osd.0 has an ID of 0.

  • On a Ceph Object Gateway node:

    Starting:

    [root@rgw ~]# systemctl start ceph-radosgw@rgw.OBJ_GATEWAY_HOST_NAME

    Stopping:

    [root@rgw ~]# systemctl stop ceph-radosgw@rgw.OBJ_GATEWAY_HOST_NAME

    Restarting:

    [root@rgw ~]# systemctl restart ceph-radosgw@rgw.OBJ_GATEWAY_HOST_NAME

    Replace

    • OBJ_GATEWAY_HOST_NAME with the name of the Ceph Object Gateway node.

2.6. Starting, stopping, and restarting Ceph daemons that run in containers

Use the systemctl command start, stop, or restart Ceph daemons that run in containers.

Prerequisites

  • Installation of the Red Hat Ceph Storage software.
  • Root-level access to the node.

Procedure

  1. To start, stop, or restart a Ceph daemon running in a container, run a systemctl command as root composed in the following format:

    systemctl ACTION ceph-DAEMON@ID
    Replace
    • ACTION is the action to perform; start, stop, or restart.
    • DAEMON is the daemon; osd, mon, mds, or rgw.
    • ID is either:

      • The short host name where the ceph-mon, ceph-mds, or ceph-rgw daemons are running.
      • The ID of the ceph-osd daemon if it was deployed.

    For example, to restart a ceph-osd daemon with the ID osd01:

    [root@osd ~]# systemctl restart ceph-osd@osd01

    To start a ceph-mon demon that runs on the ceph-monitor01 host:

    [root@mon ~]# systemctl start ceph-mon@ceph-monitor01

    To stop a ceph-rgw daemon that runs on the ceph-rgw01 host:

    [root@rgw ~]# systemctl stop ceph-radosgw@ceph-rgw01
  2. Verify that the action was completed successfully.

    systemctl status ceph-DAEMON@ID

    For example:

    [root@mon ~]# systemctl status ceph-mon@ceph-monitor01

Additional Resources

2.7. Viewing log files of Ceph daemons that run in containers

Use the journald daemon from the container host to view a log file of a Ceph daemon from a container.

Prerequisites

  • Installation of the Red Hat Ceph Storage software.
  • Root-level access to the node.

Procedure

  1. To view the entire Ceph log file, run a journalctl command as root composed in the following format:

    journalctl -u ceph-DAEMON@ID
    Replace
    • DAEMON is the Ceph daemon; osd, mon, or rgw.
    • ID is either:

      • The short host name where the ceph-mon, ceph-mds, or ceph-rgw daemons are running.
      • The ID of the ceph-osd daemon if it was deployed.

    For example, to view the entire log for the ceph-osd daemon with the ID osd01:

    [root@osd ~]# journalctl -u ceph-osd@osd01
  2. To show only the recent journal entries, use the -f option.

    journalctl -fu ceph-DAEMON@ID

    For example, to view only recent journal entries for the ceph-mon daemon that runs on the ceph-monitor01 host:

    [root@mon ~]# journalctl -fu ceph-mon@ceph-monitor01
Note

You can also use the sosreport utility to view the journald logs. For more details about SOS reports, see the What is an sosreport and how to create one in Red Hat Enterprise Linux? solution on the Red Hat Customer Portal.

Additional Resources

  • The journalctl(1) manual page.

2.8. Powering down and rebooting Red Hat Ceph Storage cluster

Follow the below procedure for powering down and rebooting the Ceph cluster.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Having root access.

Procedure

Powering down the Red Hat Ceph Storage cluster

  1. Stop the clients from using the RBD images and RADOS Gateway on this cluster and any other clients.
  2. The cluster must be in healthy state (Health_OK and all PGs active+clean) before proceeding. Run ceph status on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller nodes, to ensure the cluster is healthy.
  3. If you use the Ceph File System (CephFS), the CephFS cluster must be brought down. Taking a CephFS cluster down is done by reducing the number of ranks to 1, setting the cluster_down flag, and then failing the last rank.

    Example:

    [root@osd ~]# ceph fs set FS_NAME max_mds 1
    [root@osd ~]# ceph mds deactivate FS_NAME:1 # rank 2 of 2
    [root@osd ~]# ceph status # wait for rank 1 to finish stopping
    [root@osd ~]# ceph fs set FS_NAME cluster_down true
    [root@osd ~]# ceph mds fail FS_NAME:0

    Setting the cluster_down flag prevents standbys from taking over the failed rank.

  4. Set the noout, norecover, norebalance, nobackfill, nodown and pause flags. Run the following on a node with the client keyrings. For example, the Ceph Monitor or OpenStack controller node:

    [root@mon ~]# ceph osd set noout
    [root@mon ~]# ceph osd set norecover
    [root@mon ~]# ceph osd set norebalance
    [root@mon ~]# ceph osd set nobackfill
    [root@mon ~]# ceph osd set nodown
    [root@mon ~]# ceph osd set pause
  5. Shut down the OSD nodes one by one:

    [root@osd ~]# systemctl stop ceph-osd.target
  6. Shut down the monitor nodes one by one:

    [root@mon ~]# systemctl stop ceph-mon.target

Rebooting the Red Hat Ceph Storage cluster

  1. Power on the administration node.
  2. Power on the monitor nodes:

    [root@mon ~]# systemctl start ceph-mon.target
  3. Power on the OSD nodes:

    [root@osd ~]# systemctl start ceph-osd.target
  4. Wait for all the nodes to come up. Verify all the services are up and the connectivity is fine between the nodes.
  5. Unset the noout, norecover, norebalance, nobackfill, nodown and pause flags. Run the following on a node with the client keyrings. For example, the Ceph Monitor or OpenStack controller node:

    [root@mon ~]# ceph osd unset noout
    [root@mon ~]# ceph osd unset norecover
    [root@mon ~]# ceph osd unset norebalance
    [root@mon ~]# ceph osd unset nobackfill
    [root@mon ~]# ceph osd unset nodown
    [root@mon ~]# ceph osd unset pause
  6. If you use the Ceph File System (CephFS), the CephFS cluster must be brought back up by setting the cluster_down flag to false:

    [root@admin~]# ceph fs set FS_NAME cluster_down false
  7. Verify the cluster is in healthy state (Health_OK and all PGs active+clean). Run ceph status on a node with the client keyrings. For example, the Ceph Monitor or OpenStack controller nodes, to ensure the cluster is healthy.

2.9. Additional Resources

Chapter 3. Monitoring a Ceph storage cluster

As a storage administrator, you can monitor the overall health of the Red Hat Ceph Storage cluster, along with monitoring the health of the individual components of Ceph.

Once you have a running Red Hat Ceph Storage cluster, you might begin monitoring the storage cluster to ensure that the Ceph Monitor and Ceph OSD daemons are running, at a high-level. Ceph storage cluster clients connect to a Ceph Monitor and receive the latest version of the storage cluster map before they can read and write data to the Ceph pools within the storage cluster. So the monitor cluster must have agreement on the state of the cluster before Ceph clients can read and write data.

Ceph OSDs must peer the placement groups on the primary OSD with the copies of the placement groups on secondary OSDs. If faults arise, peering will reflect something other than the active + clean state.

3.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

3.2. High-level monitoring of a Ceph storage cluster

As a storage administrator, you can monitor the health of the Ceph daemons to ensure that they are up and running. High level monitoring also involves checking the storage cluster capacity to ensure that the storage cluster does not exceed its full ratio. The Red Hat Ceph Storage Dashboard is the most common way to conduct high-level monitoring. However, you can also use the command-line interface, the Ceph admin socket or the Ceph API to monitor the storage cluster.

3.2.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

3.2.2. Using the Ceph command interface interactively

You can interactively interface with the Ceph storage cluster by using the ceph command-line utility.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To run the ceph utility in interactive mode.

    1. Bare-metal deployments:

      Example

      [root@mon ~]# ceph
      ceph> health
      ceph> status
      ceph> quorum_status
      ceph> mon_status

    2. Container deployments:

      Red Hat Enterprise Linux 7

      docker exec -it ceph-mon-MONITOR_NAME /bin/bash

      Red Hat Enterprise Linux 8

      podman exec -it ceph-mon-MONITOR_NAME /bin/bash

      Replace
      • MONITOR_NAME with the name of the Ceph Monitor container, found by running the docker ps or podman ps command respectively.

        Example

        [root@container-host ~]# podman exec -it ceph-mon-mon01 /bin/bash

        This example opens an interactive terminal session on mon01, where you can start the Ceph interactive shell.

3.2.3. Checking the storage cluster health

After you start the Ceph storage cluster, and before you start reading or writing data, check the storage cluster’s health first.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. You can check on the health of the Ceph storage cluster with the following:

    [root@mon ~]# ceph health
  2. If you specified non-default locations for the configuration or keyring, you can specify their locations:

    [root@mon ~]# ceph -c /path/to/conf -k /path/to/keyring health

Upon starting the Ceph cluster, you will likely encounter a health warning such as HEALTH_WARN XXX num placement groups stale. Wait a few moments and check it again. When the storage cluster is ready, ceph health should return a message such as HEALTH_OK. At that point, it is okay to begin using the cluster.

3.2.4. Watching storage cluster events

You can watch events that are happening with the Ceph storage cluster using the command-line interface.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To watch the cluster’s ongoing events on the command line, open a new terminal, and then enter:

    [root@mon ~]# ceph -w

    Ceph will print each event. For example, a tiny Ceph cluster consisting of one monitor and two OSDs may print the following:

    cluster b370a29d-9287-4ca3-ab57-3d824f65e339
     health HEALTH_OK
     monmap e1: 1 mons at {ceph1=10.0.0.8:6789/0}, election epoch 2, quorum 0 ceph1
     osdmap e63: 2 osds: 2 up, 2 in
      pgmap v41338: 952 pgs, 20 pools, 17130 MB data, 2199 objects
            115 GB used, 167 GB / 297 GB avail
                 952 active+clean
    
    2014-06-02 15:45:21.655871 osd.0 [INF] 17.71 deep-scrub ok
    2014-06-02 15:45:47.880608 osd.1 [INF] 1.0 scrub ok
    2014-06-02 15:45:48.865375 osd.1 [INF] 1.3 scrub ok
    2014-06-02 15:45:50.866479 osd.1 [INF] 1.4 scrub ok
    2014-06-02 15:45:01.345821 mon.0 [INF] pgmap v41339: 952 pgs: 952 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
    2014-06-02 15:45:05.718640 mon.0 [INF] pgmap v41340: 952 pgs: 1 active+clean+scrubbing+deep, 951 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
    2014-06-02 15:45:53.997726 osd.1 [INF] 1.5 scrub ok
    2014-06-02 15:45:06.734270 mon.0 [INF] pgmap v41341: 952 pgs: 1 active+clean+scrubbing+deep, 951 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
    2014-06-02 15:45:15.722456 mon.0 [INF] pgmap v41342: 952 pgs: 952 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
    2014-06-02 15:46:06.836430 osd.0 [INF] 17.75 deep-scrub ok
    2014-06-02 15:45:55.720929 mon.0 [INF] pgmap v41343: 952 pgs: 1 active+clean+scrubbing+deep, 951 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail

    The output provides:

    • Cluster ID
    • Cluster health status
    • The monitor map epoch and the status of the monitor quorum
    • The OSD map epoch and the status of OSDs
    • The placement group map version
    • The number of placement groups and pools
    • The notional amount of data stored and the number of objects stored
    • The total amount of data stored

3.2.5. How Ceph calculates data usage

The used value reflects the actual amount of raw storage used. The xxx GB / xxx GB value means the amount available, the lesser of the two numbers, of the overall storage capacity of the cluster. The notional number reflects the size of the stored data before it is replicated, cloned or snapshotted. Therefore, the amount of data actually stored typically exceeds the notional amount stored, because Ceph creates replicas of the data and may also use storage capacity for cloning and snapshotting.

3.2.6. Understanding the storage clusters usage stats

To check a cluster’s data usage and data distribution among pools, use the df option. It is similar to the Linux df command. Execute the following:

[root@mon ~]# ceph df
RAW STORAGE:
    CLASS     SIZE        AVAIL       USED       RAW USED     %RAW USED
    hdd       662 TiB     611 TiB     51 TiB       51 TiB          7.74
    TOTAL     662 TiB     611 TiB     51 TiB       51 TiB          7.74

POOLS:
    POOL                     ID    STORED    OBJECTS   USED     %USED   MAX AVAIL
    default.rgw.users.keys   276       0 B         0       0 B      0     193 TiB
    default.rgw.data.root    277       0 B         0       0 B      0     193 TiB
    .rgw.root                278   5.7 KiB        12   2.2 MiB      0     193 TiB
    default.rgw.control      279       0 B         8       0 B      0     193 TiB
    default.rgw.gc           280       0 B         0       0 B      0     193 TiB

The RAW STORAGE section of the output provides an overview of the amount of storage the storage cluster uses for data.

  • CLASS: The type of devices used.
  • SIZE: The overall storage capacity of the storage cluster.
  • AVAIL: The amount of free space available in the storage cluster.
  • USED: The amount of used space in the storage cluster.
  • RAW USED: The sum of USED space and the space allocated the db and wal BlueStore partitions.
  • % RAW USED: The percentage of of RAW USED. Use this number in conjunction with the full ratio and near full ratio to ensure that you are not reaching the storage cluster’s capacity.

The POOLS section of the output provides a list of pools and the notional usage of each pool. The output from this section DOES NOT reflect replicas, clones or snapshots. For example, if you store an object with 1 MB of data, the notional usage will be 1 MB, but the actual usage may be 3 MB or more depending on the number of replicas for example, size = 3, clones and snapshots.

  • POOL: The name of the pool.
  • ID: The pool ID.
  • STORED: The amount of data stored by the user.
  • OBJECTS: The notional number of objects stored per pool.
  • USED: The notional amount of data stored in kilobytes, unless the number appends M for megabytes or G for gigabytes.
  • %USED: The notional percentage of storage used per pool.
  • MAX AVAIL: The maximum available space in a pool.
Note

The numbers in the POOLS section are notional. They are not inclusive of the number of replicas, snapshots or clones. As a result, the sum of the USED and %USED amounts will not add up to the RAW USED and %RAW USED amounts in the GLOBAL section of the output.

Additional Resources

3.2.7. Understanding the OSD usage stats

Use the ceph osd df command to view OSD utilization stats.

[root@mon]# ceph osd df
ID CLASS WEIGHT  REWEIGHT SIZE    USE     DATA    OMAP    META    AVAIL   %USE VAR  PGS
 3   hdd 0.90959  1.00000  931GiB 70.1GiB 69.1GiB      0B    1GiB  861GiB 7.53 2.93  66
 4   hdd 0.90959  1.00000  931GiB 1.30GiB  308MiB      0B    1GiB  930GiB 0.14 0.05  59
 0   hdd 0.90959  1.00000  931GiB 18.1GiB 17.1GiB      0B    1GiB  913GiB 1.94 0.76  57
MIN/MAX VAR: 0.02/2.98  STDDEV: 2.91
  • ID: The name of the OSD.
  • CLASS: The type of devices the OSD uses.
  • WEIGHT: The weight of the OSD in the CRUSH map.
  • REWEIGHT: The default reweight value.
  • SIZE: The overall storage capacity of the OSD.
  • USE: The OSD capacity.
  • DATA: The amount of OSD capacity that is used by user data.
  • OMAP: An estimate value of the bluefs storage that is being used to store object map (omap) data (key value pairs stored in rocksdb).
  • META: The bluefs space allocated, or the value set in the bluestore_bluefs_min parameter, whichever is larger, for internal metadata which is calculated as the total space allocated in bluefs minus the estimated omap data size.
  • AVAIL: The amount of free space available on the OSD.
  • %USE: The notional percentage of storage used by the OSD
  • VAR: The variation above or below average utilization.
  • PGS: The number of placement groups in the OSD.
  • MIN/MAX VAR: The minimum and maximum variation across all OSDs.

Additional Resources

3.2.8. Checking the Red Hat Ceph Storage cluster status

You can check the status of the Red Hat Ceph Storage cluster from the command-line interface. The status sub command or the -s argument will display the current status of the storage cluster.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To check a storage cluster’s status, execute the following:

    [root@mon ~]# ceph status

    Or:

    [root@mon ~]# ceph -s
  2. In interactive mode, type status and press Enter:

    [root@mon ~]# ceph> status

    For example, a tiny Ceph cluster consisting of one monitor, and two OSDs can print the following:

    cluster b370a29d-9287-4ca3-ab57-3d824f65e339
     health HEALTH_OK
     monmap e1: 1 mons at {ceph1=10.0.0.8:6789/0}, election epoch 2, quorum 0 ceph1
     osdmap e63: 2 osds: 2 up, 2 in
      pgmap v41332: 952 pgs, 20 pools, 17130 MB data, 2199 objects
            115 GB used, 167 GB / 297 GB avail
                   1 active+clean+scrubbing+deep
                 951 active+clean

3.2.9. Checking the Ceph Monitor status

If the storage cluster has multiple Ceph Monitors, which is a requirement for a production Red Hat Ceph Storage cluster, then check the Ceph Monitor quorum status after starting the storage cluster, and before doing any reading or writing of data.

A quorum must be present when multiple monitors are running.

Check Ceph Monitor status periodically to ensure that they are running. If there is a problem with the Ceph Monitor, that prevents an agreement on the state of the storage cluster, the fault may prevent Ceph clients from reading and writing data.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To display the monitor map, execute the following:

    [root@mon ~]# ceph mon stat

    or

    [root@mon ~]# ceph mon dump
  2. To check the quorum status for the storage cluster, execute the following:

    [root@mon ~]# ceph quorum_status -f json-pretty

    Ceph will return the quorum status. A Red Hat Ceph Storage cluster consisting of three monitors may return the following:

    Example

    { "election_epoch": 10,
      "quorum": [
            0,
            1,
            2],
      "monmap": { "epoch": 1,
          "fsid": "444b489c-4f16-4b75-83f0-cb8097468898",
          "modified": "2011-12-12 13:28:27.505520",
          "created": "2011-12-12 13:28:27.505520",
          "mons": [
                { "rank": 0,
                  "name": "a",
                  "addr": "127.0.0.1:6789\/0"},
                { "rank": 1,
                  "name": "b",
                  "addr": "127.0.0.1:6790\/0"},
                { "rank": 2,
                  "name": "c",
                  "addr": "127.0.0.1:6791\/0"}
               ]
        }
    }

3.2.10. Using the Ceph administration socket

Use the administration socket to interact with a given daemon directly by using a UNIX socket file. For example, the socket enables you to:

  • List the Ceph configuration at runtime
  • Set configuration values at runtime directly without relying on Monitors. This is useful when Monitors are down.
  • Dump historic operations
  • Dump the operation priority queue state
  • Dump operations without rebooting
  • Dump performance counters

In addition, using the socket is helpful when troubleshooting problems related to Monitors or OSDs.

Important

The administration socket is only available while a daemon is running. When you shut down the daemon properly, the administration socket is removed. However, if the daemon terminates unexpectedly, the administration socket might persist.

Regardless, if the daemon is not running, a following error is returned when attempting to use the administration socket:

Error 111: Connection Refused

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To use the socket:

    Syntax

    [root@mon ~]# ceph daemon TYPE.ID COMMAND

    Replace:

    • TYPE with the type of the Ceph daemon (mon, osd, mds).
    • ID with the daemon ID
    • COMMAND with the command to run. Use help to list the available commands for a given daemon.

      Example

      To view a Monitor status of a Ceph Monitor named mon.0:

      [root@mon ~]# ceph daemon mon.0 mon_status
  2. Alternatively, specify the Ceph daemon by using its socket file:

    ceph daemon /var/run/ceph/SOCKET_FILE COMMAND
  3. To view the status of an Ceph OSD named osd.2:

    [root@mon ~]# ceph daemon /var/run/ceph/ceph-osd.2.asok status
  4. To list all socket files for the Ceph processes:

    [root@mon ~]# ls /var/run/ceph

Additional Resources

3.2.11. Understanding the Ceph OSD status

An OSD’s status is either in the cluster, in, or out of the cluster, out. It is either up and running, up, or it is down and not running, or down. If an OSD is up, it may be either in the storage cluster, where data can be read and written, or it is out of the storage cluster. If it was in the cluster and recently moved out of the cluster, Ceph will migrate placement groups to other OSDs. If an OSD is out of the cluster, CRUSH will not assign placement groups to the OSD. If an OSD is down, it should also be out.

Note

If an OSD is down and in, there is a problem and the cluster will not be in a healthy state.

OSD States

If you execute a command such as ceph health, ceph -s or ceph -w, you may notice that the cluster does not always echo back HEALTH OK. Don’t panic. With respect to OSDs, you should expect that the cluster will NOT echo HEALTH OK in a few expected circumstances:

  • You haven’t started the cluster yet, it won’t respond.
  • You have just started or restarted the cluster and it’s not ready yet, because the placement groups are getting created and the OSDs are in the process of peering.
  • You just added or removed an OSD.
  • You just have modified the cluster map.

An important aspect of monitoring OSDs is to ensure that when the cluster is up and running that all OSDs that are in the cluster are up and running, too.

To see if all OSDs are running, execute:

[root@mon ~]# ceph osd stat

or

[root@mon ~]# ceph osd dump

The result should tell you the map epoch, eNNNN, the total number of OSDs, x, how many, y, are up, and how many, z, are in:

eNNNN: x osds: y up, z in

If the number of OSDs that are in the cluster is more than the number of OSDs that are up. Execute the following command to identify the ceph-osd daemons that aren’t running:

[root@mon ~]# ceph osd tree

Example

# id    weight  type name   up/down reweight
-1  3   pool default
-3  3       rack mainrack
-2  3           host osd-host
0   1               osd.0   up  1
1   1               osd.1   up  1
2   1               osd.2   up  1

Tip

The ability to search through a well-designed CRUSH hierarchy may help you troubleshoot the storage cluster by identifying the physical locations faster.

If an OSD is down, connect to the node and start it. You can use Red Hat Storage Console to restart the OSD node, or you can use the command line.

Example

[root@mon ~]# systemctl start ceph-osd@OSD_ID

3.2.12. Additional Resources

3.3. Low-level monitoring of a Ceph storage cluster

As a storage administrator, you can monitor the health of a Red Hat Ceph Storage cluster from a low-level perspective. Low-level monitoring typically involves ensuring that Ceph OSDs are peering properly. When peering faults occur, placement groups operate in a degraded state. This degraded state can be the result of many different things, such as hardware failure, a hung or crashed Ceph daemon, network latency, or a complete site outage.

3.3.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

3.3.2. Monitoring Placement Group Sets

When CRUSH assigns placement groups to OSDs, it looks at the number of replicas for the pool and assigns the placement group to OSDs such that each replica of the placement group gets assigned to a different OSD. For example, if the pool requires three replicas of a placement group, CRUSH may assign them to osd.1, osd.2 and osd.3 respectively. CRUSH actually seeks a pseudo-random placement that will take into account failure domains you set in the CRUSH map, so you will rarely see placement groups assigned to nearest neighbor OSDs in a large cluster. We refer to the set of OSDs that should contain the replicas of a particular placement group as the Acting Set. In some cases, an OSD in the Acting Set is down or otherwise not able to service requests for objects in the placement group. When these situations arise, don’t panic. Common examples include:

  • You added or removed an OSD. Then, CRUSH reassigned the placement group to other OSDs—​thereby changing the composition of the Acting Set and spawning the migration of data with a "backfill" process.
  • An OSD was down, was restarted and is now recovering.
  • An OSD in the Acting Set is down or unable to service requests, and another OSD has temporarily assumed its duties.

Ceph processes a client request using the Up Set, which is the set of OSDs that will actually handle the requests. In most cases, the Up Set and the Acting Set are virtually identical. When they are not, it may indicate that Ceph is migrating data, an OSD is recovering, or that there is a problem, that is, Ceph usually echoes a HEALTH WARN state with a "stuck stale" message in such scenarios.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To retrieve a list of placement groups:

    [root@mon ~]# ceph pg dump
  2. To view which OSDs are in the Acting Set or in the Up Set for a given placement group:

    [root@mon ~]# ceph pg map PG_NUM

    The result should tell you the osdmap epoch, eNNN, the placement group number, PG_NUM, the OSDs in the Up Set up[], and the OSDs in the acting set, acting[]:

    [root@mon ~]# ceph osdmap eNNN pg PG_NUM-> up [0,1,2] acting [0,1,2]
    Note

    If the Up Set and Acting Set do not match, this may be an indicator that the cluster rebalancing itself or of a potential problem with the cluster.

3.3.3. Ceph OSD peering

Before you can write data to a placement group, it must be in an active state, and it should be in a clean state. For Ceph to determine the current state of a placement group, the primary OSD of the placement group that is, the first OSD in the acting set, peers with the secondary and tertiary OSDs to establish agreement on the current state of the placement group. Assuming a pool with 3 replicas of the PG.

Peering

3.3.4. Placement Group States

If you execute a command such as ceph health, ceph -s or ceph -w, you may notice that the cluster does not always echo back HEALTH OK. After you check to see if the OSDs are running, you should also check placement group states. You should expect that the cluster will NOT echo HEALTH OK in a number of placement group peering-related circumstances:

  • You have just created a pool and placement groups haven’t peered yet.
  • The placement groups are recovering.
  • You have just added an OSD to or removed an OSD from the cluster.
  • You have just modified the CRUSH map and the placement groups are migrating.
  • There is inconsistent data in different replicas of a placement group.
  • Ceph is scrubbing a placement group’s replicas.
  • Ceph doesn’t have enough storage capacity to complete backfilling operations.

If one of the foregoing circumstances causes Ceph to echo HEALTH WARN, don’t panic. In many cases, the cluster will recover on its own. In some cases, you may need to take action. An important aspect of monitoring placement groups is to ensure that when the cluster is up and running that all placement groups are active, and preferably in the clean state.

To see the status of all placement groups, execute:

[root@mon ~]# ceph pg stat

The result should tell you the placement group map version, vNNNNNN, the total number of placement groups, x, and how many placement groups, y, are in a particular state such as active+clean:

vNNNNNN: x pgs: y active+clean; z bytes data, aa MB used, bb GB / cc GB avail
Note

It is common for Ceph to report multiple states for placement groups.

Snapshot Trimming PG States

When snapshots exist, two additional PG states will be reported.

  • snaptrim : The PGs are currently being trimmed
  • snaptrim_wait : The PGs are waiting to be trimmed

Example Output:

244 active+clean+snaptrim_wait
 32 active+clean+snaptrim

In addition to the placement group states, Ceph will also echo back the amount of data used, aa, the amount of storage capacity remaining, bb, and the total storage capacity for the placement group. These numbers can be important in a few cases:

  • You are reaching the near full ratio or full ratio.
  • Your data isn’t getting distributed across the cluster due to an error in the CRUSH configuration.

Placement Group IDs

Placement group IDs consist of the pool number, and not the pool name, followed by a period (.) and the placement group ID—​a hexadecimal number. You can view pool numbers and their names from the output of ceph osd lspools. The default pool names data, metadata and rbd correspond to pool numbers 0, 1 and 2 respectively. A fully qualified placement group ID has the following form:

POOL_NUM.PG_ID

Example output:

0.1f
  • To retrieve a list of placement groups:

    [root@mon ~]# ceph pg dump
  • To format the output in JSON format and save it to a file:

    [root@mon ~]# ceph pg dump -o FILE_NAME --format=json
  • To query a particular placement group:

    [root@mon ~]# ceph pg POOL_NUM.PG_ID query

    Example output in JSON format:

    {
      "state": "active+clean",
      "up": [
        1,
        0
      ],
      "acting": [
        1,
        0
      ],
      "info": {
        "pgid": "1.e",
        "last_update": "4'1",
        "last_complete": "4'1",
        "log_tail": "0'0",
        "last_backfill": "MAX",
        "purged_snaps": "[]",
        "history": {
          "epoch_created": 1,
          "last_epoch_started": 537,
          "last_epoch_clean": 537,
          "last_epoch_split": 534,
          "same_up_since": 536,
          "same_interval_since": 536,
          "same_primary_since": 536,
          "last_scrub": "4'1",
          "last_scrub_stamp": "2013-01-25 10:12:23.828174"
        },
        "stats": {
          "version": "4'1",
          "reported": "536'782",
          "state": "active+clean",
          "last_fresh": "2013-01-25 10:12:23.828271",
          "last_change": "2013-01-25 10:12:23.828271",
          "last_active": "2013-01-25 10:12:23.828271",
          "last_clean": "2013-01-25 10:12:23.828271",
          "last_unstale": "2013-01-25 10:12:23.828271",
          "mapping_epoch": 535,
          "log_start": "0'0",
          "ondisk_log_start": "0'0",
          "created": 1,
          "last_epoch_clean": 1,
          "parent": "0.0",
          "parent_split_bits": 0,
          "last_scrub": "4'1",
          "last_scrub_stamp": "2013-01-25 10:12:23.828174",
          "log_size": 128,
          "ondisk_log_size": 128,
          "stat_sum": {
            "num_bytes": 205,
            "num_objects": 1,
            "num_object_clones": 0,
            "num_object_copies": 0,
            "num_objects_missing_on_primary": 0,
            "num_objects_degraded": 0,
            "num_objects_unfound": 0,
            "num_read": 1,
            "num_read_kb": 0,
            "num_write": 3,
            "num_write_kb": 1
          },
          "stat_cat_sum": {
    
          },
          "up": [
            1,
            0
          ],
          "acting": [
            1,
            0
          ]
        },
        "empty": 0,
        "dne": 0,
        "incomplete": 0
      },
      "recovery_state": [
        {
          "name": "Started\/Primary\/Active",
          "enter_time": "2013-01-23 09:35:37.594691",
          "might_have_unfound": [
    
          ],
          "scrub": {
            "scrub_epoch_start": "536",
            "scrub_active": 0,
            "scrub_block_writes": 0,
            "finalizing_scrub": 0,
            "scrub_waiting_on": 0,
            "scrub_waiting_on_whom": [
    
            ]
          }
        },
        {
          "name": "Started",
          "enter_time": "2013-01-23 09:35:31.581160"
        }
      ]
    }

Additional Resources

  • See the chapter Object Storage Daemon (OSD) configuration options in the Red Hat Ceph Storage 4 Configuration Guide for more details on the snapshot trimming settings.

3.3.5. Placement Group creating state

When you create a pool, it will create the number of placement groups you specified. Ceph will echo creating when it is creating one or more placement groups. Once they are created, the OSDs that are part of a placement group’s Acting Set will peer. Once peering is complete, the placement group status should be active+clean, which means a Ceph client can begin writing to the placement group.

Creating PGs

3.3.6. Placement group peering state

When Ceph is Peering a placement group, Ceph is bringing the OSDs that store the replicas of the placement group into agreement about the state of the objects and metadata in the placement group. When Ceph completes peering, this means that the OSDs that store the placement group agree about the current state of the placement group. However, completion of the peering process does NOT mean that each replica has the latest contents.

Authoritative History

Ceph will NOT acknowledge a write operation to a client, until all OSDs of the acting set persist the write operation. This practice ensures that at least one member of the acting set will have a record of every acknowledged write operation since the last successful peering operation.

With an accurate record of each acknowledged write operation, Ceph can construct and disseminate a new authoritative history of the placement group. A complete, and fully ordered set of operations that, if performed, would bring an OSD’s copy of a placement group up to date.

3.3.7. Placement group active state

Once Ceph completes the peering process, a placement group may become active. The active state means that the data in the placement group is generally available in the primary placement group and the replicas for read and write operations.

3.3.8. Placement Group clean state

When a placement group is in the clean state, the primary OSD and the replica OSDs have successfully peered and there are no stray replicas for the placement group. Ceph replicated all objects in the placement group the correct number of times.

3.3.9. Placement Group degraded state

When a client writes an object to the primary OSD, the primary OSD is responsible for writing the replicas to the replica OSDs. After the primary OSD writes the object to storage, the placement group will remain in a degraded state until the primary OSD has received an acknowledgement from the replica OSDs that Ceph created the replica objects successfully.

The reason a placement group can be active+degraded is that an OSD may be active even though it doesn’t hold all of the objects yet. If an OSD goes down, Ceph marks each placement group assigned to the OSD as degraded. The OSDs must peer again when the OSD comes back online. However, a client can still write a new object to a degraded placement group if it is active.

If an OSD is down and the degraded condition persists, Ceph may mark the down OSD as out of the cluster and remap the data from the down OSD to another OSD. The time between being marked down and being marked out is controlled by mon osd down out interval, which is set to 300 seconds by default.

A placement group can also be degraded, because Ceph cannot find one or more objects that Ceph thinks should be in the placement group. While you cannot read or write to unfound objects, you can still access all of the other objects in the degraded placement group.

Let’s say there are 9 OSDs in a three way replica pool. If OSD number 9 goes down, the PGs assigned to OSD 9 go in a degraded state. If OSD 9 doesn’t recover, it goes out of the cluster and the cluster rebalances. In that scenario, the PGs are degraded and then recover to an active state.

3.3.10. Placement Group recovering state

Ceph was designed for fault-tolerance at a scale where hardware and software problems are ongoing. When an OSD goes down, its contents may fall behind the current state of other replicas in the placement groups. When the OSD is back up, the contents of the placement groups must be updated to reflect the current state. During that time period, the OSD may reflect a recovering state.

Recovery isn’t always trivial, because a hardware failure might cause a cascading failure of multiple OSDs. For example, a network switch for a rack or cabinet may fail, which can cause the OSDs of a number of host machines to fall behind the current state of the cluster. Each one of the OSDs must recover once the fault is resolved.

Ceph provides a number of settings to balance the resource contention between new service requests and the need to recover data objects and restore the placement groups to the current state. The osd recovery delay start setting allows an OSD to restart, re-peer and even process some replay requests before starting the recovery process. The osd recovery threads setting limits the number of threads for the recovery process, by default one thread. The osd recovery thread timeout sets a thread timeout, because multiple OSDs may fail, restart and re-peer at staggered rates. The osd recovery max active setting limits the number of recovery requests an OSD will entertain simultaneously to prevent the OSD from failing to serve . The osd recovery max chunk setting limits the size of the recovered data chunks to prevent network congestion.

3.3.11. Back fill state

When a new OSD joins the cluster, CRUSH will reassign placement groups from OSDs in the cluster to the newly added OSD. Forcing the new OSD to accept the reassigned placement groups immediately can put excessive load on the new OSD. Backfilling the OSD with the placement groups allows this process to begin in the background. Once backfilling is complete, the new OSD will begin serving requests when it is ready.

During the backfill operations, you may see one of several states: * backfill_wait indicates that a backfill operation is pending, but isn’t underway yet * backfill indicates that a backfill operation is underway * backfill_too_full indicates that a backfill operation was requested, but couldn’t be completed due to insufficient storage capacity.

When a placement group cannot be backfilled, it may be considered incomplete.

Ceph provides a number of settings to manage the load spike associated with reassigning placement groups to an OSD, especially a new OSD. By default, osd_max_backfills sets the maximum number of concurrent backfills to or from an OSD to 10. The osd backfill full ratio enables an OSD to refuse a backfill request if the OSD is approaching its full ratio, by default 85%. If an OSD refuses a backfill request, the osd backfill retry interval enables an OSD to retry the request, by default after 10 seconds. OSDs can also set osd backfill scan min and osd backfill scan max to manage scan intervals, by default 64 and 512.

For some workloads, it is beneficial to avoid regular recovery entirely and use backfill instead. Since backfilling occurs in the background, this allows I/O to proceed on the objects in the OSD. To force backfill rather than recovery, set osd_min_pg_log_entries to 1, and set osd_max_pg_log_entries to 2. Contact your Red Hat Support account team for details on when this situation is appropriate for your workload.

3.3.12. Placement Group remapped state

When the Acting Set that services a placement group changes, the data migrates from the old acting set to the new acting set. It may take some time for a new primary OSD to service requests. So it may ask the old primary to continue to service requests until the placement group migration is complete. Once data migration completes, the mapping uses the primary OSD of the new acting set.

3.3.13. Placement Group stale state

While Ceph uses heartbeats to ensure that hosts and daemons are running, the ceph-osd daemons may also get into a stuck state where they aren’t reporting statistics in a timely manner. For example, a temporary network fault. By default, OSD daemons report their placement group, up thru, boot and failure statistics every half second, that is, 0.5, which is more frequent than the heartbeat thresholds. If the Primary OSD of a placement group’s acting set fails to report to the monitor or if other OSDs have reported the primary OSD down, the monitors will mark the placement group stale.

When you start the storage cluster, it is common to see the stale state until the peering process completes. After the storage cluster has been running for awhile, seeing placement groups in the stale state indicates that the primary OSD for those placement groups is down or not reporting placement group statistics to the monitor.

3.3.14. Placement Group misplaced state

There are some temporary backfilling scenarios where a PG gets mapped temporarily to an OSD. When that temporary situation should no longer be the case, the PGs might still reside in the temporary location and not in the proper location. In which case, they are said to be misplaced. That’s because the correct number of extra copies actually exist, but one or more copies is in the wrong place.

For example, there are 3 OSDs: 0,1,2 and all PGs map to some permutation of those three. If you add another OSD (OSD 3), some PGs will now map to OSD 3 instead of one of the others. However, until OSD 3 is backfilled, the PG will have a temporary mapping allowing it to continue to serve I/O from the old mapping. During that time, the PG is misplaced, because it has a temporary mapping, but not degraded, since there are 3 copies.

Example

pg 1.5: up=acting: [0,1,2]
ADD_OSD_3
pg 1.5: up: [0,3,1] acting: [0,1,2]

[0,1,2] is a temporary mapping, so the up set is not equal to the acting set and the PG is misplaced but not degraded since [0,1,2] is still three copies.

Example

pg 1.5: up=acting: [0,3,1]

OSD 3 is now backfilled and the temporary mapping is removed, not degraded and not misplaced.

3.3.15. Placement Group incomplete state

A PG goes into a incomplete state when there is incomplete content and peering fails, that is, when there are no complete OSDs which are current enough to perform recovery.

Lets say OSD 1, 2, and 3 are the acting OSD set and it switches to OSD 1, 4, and 3, then osd.1 will request a temporary acting set of OSD 1, 2, and 3 while backfilling 4. During this time, if OSD 1, 2, and 3 all go down, osd.4 will be the only one left which might not have fully backfilled all the data. At this time, the PG will go incomplete indicating that there are no complete OSDs which are current enough to perform recovery.

Alternately, if osd.4 is not involved and the acting set is simply OSD 1, 2, and 3 when OSD 1, 2, and 3 go down, the PG would likely go stale indicating that the mons have not heard anything on that PG since the acting set changed. The reason being there are no OSDs left to notify the new OSDs.

3.3.16. Identifying stuck Placement Groups

As previously noted, a placement group isn’t necessarily problematic just because its state isn’t active+clean. Generally, Ceph’s ability to self repair may not be working when placement groups get stuck. The stuck states include:

  • Unclean: Placement groups contain objects that are not replicated the desired number of times. They should be recovering.
  • Inactive: Placement groups cannot process reads or writes because they are waiting for an OSD with the most up-to-date data to come back up.
  • Stale: Placement groups are in an unknown state, because the OSDs that host them have not reported to the monitor cluster in a while, and can be configured with the mon osd report timeout setting.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To identify stuck placement groups, execute the following:

    ceph pg dump_stuck {inactive|unclean|stale|undersized|degraded [inactive|unclean|stale|undersized|degraded...]} {<int>}

3.3.17. Finding an object’s location

The Ceph client retrieves the latest cluster map and the CRUSH algorithm calculates how to map the object to a placement group, and then calculates how to assign the placement group to an OSD dynamically.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To find the object location, all you need is the object name and the pool name:

    ceph osd map POOL_NAME OBJECT_NAME

Chapter 4. Override Ceph behavior

As a storage administrator, you need to understand how to use overrides for the Red Hat Ceph Storage cluster to change Ceph options during runtime.

4.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

4.2. Setting and unsetting Ceph override options

You can set and unset Ceph options to override Ceph’s default behavior.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To override Ceph’s default behavior, use the ceph osd set command and the behavior you wish to override:

    ceph osd set FLAG

    Once you set the behavior, ceph health will reflect the override(s) that you have set for the cluster.

  2. To cease overriding Ceph’s default behavior, use the ceph osd unset command and the override you wish to cease.

    ceph osd unset FLAG
FlagDescription

noin

Prevents OSDs from being treated as in the cluster.

noout

Prevents OSDs from being treated as out of the cluster.

noup

Prevents OSDs from being treated as up and running.

nodown

Prevents OSDs from being treated as down.

full

Makes a cluster appear to have reached its full_ratio, and thereby prevents write operations.

pause

Ceph will stop processing read and write operations, but will not affect OSD in, out, up or down statuses.

nobackfill

Ceph will prevent new backfill operations.

norebalance

Ceph will prevent new rebalancing operations.

norecover

Ceph will prevent new recovery operations.

noscrub

Ceph will prevent new scrubbing operations.

nodeep-scrub

Ceph will prevent new deep scrubbing operations.

notieragent

Ceph will disable the process that is looking for cold/dirty objects to flush and evict.

4.3. Ceph override use cases

  • noin: Commonly used with noout to address flapping OSDs.
  • noout: If the mon osd report timeout is exceeded and an OSD has not reported to the monitor, the OSD will get marked out. If this happens erroneously, you can set noout to prevent the OSD(s) from getting marked out while you troubleshoot the issue.
  • noup: Commonly used with nodown to address flapping OSDs.
  • nodown: Networking issues may interrupt Ceph 'heartbeat' processes, and an OSD may be up but still get marked down. You can set nodown to prevent OSDs from getting marked down while troubleshooting the issue.
  • full: If a cluster is reaching its full_ratio, you can pre-emptively set the cluster to full and expand capacity.

    Note

    Setting the cluster to full will prevent write operations.

  • pause: If you need to troubleshoot a running Ceph cluster without clients reading and writing data, you can set the cluster to pause to prevent client operations.
  • nobackfill: If you need to take an OSD or node down temporarily, for example, upgrading daemons, you can set nobackfill so that Ceph will not backfill while the OSDs is down.
  • norecover: If you need to replace an OSD disk and don’t want the PGs to recover to another OSD while you are hotswapping disks, you can set norecover to prevent the other OSDs from copying a new set of PGs to other OSDs.
  • noscrub and nodeep-scrubb: If you want to prevent scrubbing for example, to reduce overhead during high loads, recovery, backfilling, and rebalancing you can set noscrub and/or nodeep-scrub to prevent the cluster from scrubbing OSDs.
  • notieragent: If you want to stop the tier agent process from finding cold objects to flush to the backing storage tier, you may set notieragent.

Chapter 5. Ceph user management

As a storage administrator, you can manage the Ceph user base by providing authentication, keyring management and access control to objects in the Red Hat Ceph Storage cluster.

OSD States

5.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Access to a Ceph Monitor or Ceph client node.

5.2. Ceph user management background

When Ceph runs with authentication and authorization enabled, you must specify a user name and a keyring containing the secret key of the specified user. If you do not specify a user name, Ceph will use the client.admin administrative user as the default user name. If you do not specify a keyring, Ceph will look for a keyring by using the keyring setting in the Ceph configuration. For example, if you execute the ceph health command without specifying a user or keyring:

# ceph health

Ceph interprets the command like this:

# ceph -n client.admin --keyring=/etc/ceph/ceph.client.admin.keyring health

Alternatively, you may use the CEPH_ARGS environment variable to avoid re-entry of the user name and secret.

Irrespective of the type of Ceph client, for example, block device, object store, file system, native API, or the Ceph command line, Ceph stores all data as objects within pools. Ceph users must have access to pools in order to read and write data. Additionally, administrative Ceph users must have permissions to execute Ceph’s administrative commands.

The following concepts can help you understand Ceph user management.

Storage Cluster Users

A user of the Red Hat Ceph Storage cluster is either an individual or as an application. Creating users allows you to control who can access the storage cluster, its pools, and the data within those pools.

Ceph has the notion of a type of user. For the purposes of user management, the type will always be client. Ceph identifies users in period (.) delimited form consisting of the user type and the user ID. For example, TYPE.ID, client.admin, or client.user1. The reason for user typing is that Ceph Monitors, and OSDs also use the Cephx protocol, but they are not clients. Distinguishing the user type helps to distinguish between client users and other users—​streamlining access control, user monitoring and traceability.

Sometimes Ceph’s user type may seem confusing, because the Ceph command line allows you to specify a user with or without the type, depending upon the command line usage. If you specify --user or --id, you can omit the type. So client.user1 can be entered simply as user1. If you specify --name or -n, you must specify the type and name, such as client.user1. Red Hat recommends using the type and name as a best practice wherever possible.

Note

A Red Hat Ceph Storage cluster user is not the same as a Ceph Object Gateway user. The object gateway uses a Red Hat Ceph Storage cluster user to communicate between the gateway daemon and the storage cluster, but the gateway has its own user management functionality for its end users.

Authorization capabilities

Ceph uses the term "capabilities" (caps) to describe authorizing an authenticated user to exercise the functionality of the Ceph Monitors and OSDs. Capabilities can also restrict access to data within a pool or a namespace within a pool. A Ceph administrative user sets a user’s capabilities when creating or updating a user. Capability syntax follows the form:

Syntax

DAEMON_TYPE 'allow CAPABILITY' [DAEMON_TYPE 'allow CAPABILITY']

  • Monitor Caps: Monitor capabilities include r, w, x, allow profile CAP, and profile rbd.

    Example

    mon 'allow rwx`
    mon 'allow profile osd'

  • OSD Caps: OSD capabilities include r, w, x, class-read, class-write, profile osd, profile rbd, and profile rbd-read-only. Additionally, OSD capabilities also allow for pool and namespace settings. :

    osd 'allow CAPABILITY' [pool=POOL_NAME] [namespace=NAMESPACE_NAME]
Note

The Ceph Object Gateway daemon (radosgw) is a client of the Ceph storage cluster, so it isn’t represented as a Ceph storage cluster daemon type.

The following entries describe each capability.

allow

Precedes access settings for a daemon.

r

Gives the user read access. Required with monitors to retrieve the CRUSH map.

w

Gives the user write access to objects.

x

Gives the user the capability to call class methods (that is, both read and write) and to conduct auth operations on monitors.

class-read

Gives the user the capability to call class read methods. Subset of x.

class-write

Gives the user the capability to call class write methods. Subset of x.

*

Gives the user read, write and execute permissions for a particular daemon or pool, and the ability to execute admin commands.

profile osd

Gives a user permissions to connect as an OSD to other OSDs or monitors. Conferred on OSDs to enable OSDs to handle replication heartbeat traffic and status reporting.

profile bootstrap-osd

Gives a user permissions to bootstrap an OSD, so that they have permissions to add keys when bootstrapping an OSD.

profile rbd

Gives a user read-write access to the Ceph Block Devices.

profile rbd-read-only

Gives a user read-only access to the Ceph Block Devices.

Pool

A pool defines a storage strategy for Ceph clients, and acts as a logical partition for that strategy.

In Ceph deployments, it is common to create a pool to support different types of use cases. For example, cloud volumes or images, object storage, hot storage, cold storage, and so on. When deploying Ceph as a back end for OpenStack, a typical deployment would have pools for volumes, images, backups and virtual machines, and users such as client.glance, client.cinder, and so on.

Namespace

Objects within a pool can be associated to a namespace—​a logical group of objects within the pool. A user’s access to a pool can be associated with a namespace such that reads and writes by the user take place only within the namespace. Objects written to a namespace within the pool can only be accessed by users who have access to the namespace.

Note

Currently, namespaces are only useful for applications written on top of librados. Ceph clients such as block device and object storage do not currently support this feature.

The rationale for namespaces is that pools can be a computationally expensive method of segregating data by use case, because each pool creates a set of placement groups that get mapped to OSDs. If multiple pools use the same CRUSH hierarchy and ruleset, OSD performance may degrade as load increases.

For example, a pool should have approximately 100 placement groups per OSD. So an exemplary cluster with 1000 OSDs would have 100,000 placement groups for one pool. Each pool mapped to the same CRUSH hierarchy and ruleset would create another 100,000 placement groups in the exemplary cluster. By contrast, writing an object to a namespace simply associates the namespace to the object name with out the computational overhead of a separate pool. Rather than creating a separate pool for a user or set of users, you may use a namespace.

Note

Only available using librados at this time.

Additional Resources

5.3. Managing Ceph users

As a storage administrator, you can manage Ceph users by creating, modifying, deleting, and importing users. A Ceph client user can be either individuals or applications, which use Ceph clients to interact with the Red Hat Ceph Storage cluster daemons.

5.3.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Access to a Ceph Monitor or Ceph client node.

5.3.2. Listing Ceph users

You can list the users in the storage cluster using the command-line interface.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To list the users in the storage cluster, execute the following:

    [root@mon ~]# ceph auth list

    Ceph will list out all users in the storage cluster. For example, in a two-node exemplary storage cluster, ceph auth list will output something that looks like this:

    Example

    installed auth entries:
    
    osd.0
        key: AQCvCbtToC6MDhAATtuT70Sl+DymPCfDSsyV4w==
        caps: [mon] allow profile osd
        caps: [osd] allow *
    osd.1
        key: AQC4CbtTCFJBChAAVq5spj0ff4eHZICxIOVZeA==
        caps: [mon] allow profile osd
        caps: [osd] allow *
    client.admin
        key: AQBHCbtT6APDHhAA5W00cBchwkQjh3dkKsyPjw==
        caps: [mds] allow
        caps: [mon] allow *
        caps: [osd] allow *
    client.bootstrap-mds
        key: AQBICbtTOK9uGBAAdbe5zcIGHZL3T/u2g6EBww==
        caps: [mon] allow profile bootstrap-mds
    client.bootstrap-osd
        key: AQBHCbtT4GxqORAADE5u7RkpCN/oo4e5W0uBtw==
        caps: [mon] allow profile bootstrap-osd

Note

The TYPE.ID notation for users applies such that osd.0 is a user of type osd and its ID is 0, client.admin is a user of type client and its ID is admin, that is, the default client.admin user. Note also that each entry has a key: VALUE entry, and one or more caps: entries.

You may use the -o FILE_NAME option with ceph auth list to save the output to a file.

5.3.3. Display Ceph user information

You can display a Ceph’s user information using the command-line interface.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To retrieve a specific user, key and capabilities, execute the following:

    ceph auth export TYPE.ID

    Example

    [root@mon ~]# ceph auth get client.admin

  2. You can also use the -o FILE_NAME option with ceph auth get to save the output to a file. Developers can also execute the following:

    ceph auth export TYPE.ID

    Example

    [root@mon ~]# ceph auth export client.admin

The auth export command is identical to auth get, but also prints out the internal auid, which isn’t relevant to end users.

5.3.4. Add a new Ceph user

Adding a user creates a username, that is, TYPE.ID, a secret key and any capabilities included in the command you use to create the user.

A user’s key enables the user to authenticate with the Ceph storage cluster. The user’s capabilities authorize the user to read, write, or execute on Ceph monitors (mon), Ceph OSDs (osd) or Ceph Metadata Servers (mds).

There are a few ways to add a user:

  • ceph auth add: This command is the canonical way to add a user. It will create the user, generate a key and add any specified capabilities.
  • ceph auth get-or-create: This command is often the most convenient way to create a user, because it returns a keyfile format with the user name (in brackets) and the key. If the user already exists, this command simply returns the user name and key in the keyfile format. You may use the -o FILE_NAME option to save the output to a file.
  • ceph auth get-or-create-key: This command is a convenient way to create a user and return the user’s key only. This is useful for clients that need the key only, for example, libvirt. If the user already exists, this command simply returns the key. You may use the -o FILE_NAME option to save the output to a file.

When creating client users, you may create a user with no capabilities. A user with no capabilities is useless beyond mere authentication, because the client cannot retrieve the cluster map from the monitor. However, you can create a user with no capabilities if you wish to defer adding capabilities later using the ceph auth caps command.

A typical user has at least read capabilities on the Ceph monitor and read and write capability on Ceph OSDs. Additionally, a user’s OSD permissions are often restricted to accessing a particular pool. :

[root@mon ~]# ceph auth add client.john mon 'allow r' osd 'allow rw pool=liverpool'
[root@mon ~]# ceph auth get-or-create client.paul mon 'allow r' osd 'allow rw pool=liverpool'
[root@mon ~]# ceph auth get-or-create client.george mon 'allow r' osd 'allow rw pool=liverpool' -o george.keyring
[root@mon ~]# ceph auth get-or-create-key client.ringo mon 'allow r' osd 'allow rw pool=liverpool' -o ringo.key
Important

If you provide a user with capabilities to OSDs, but you DO NOT restrict access to particular pools, the user will have access to ALL pools in the cluster!

5.3.5. Modifying a Ceph User

The ceph auth caps command allows you to specify a user and change the user’s capabilities.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To add capabilities, use the form:

    ceph auth caps USERTYPE.USERID DAEMON 'allow [r|w|x|*|...] [pool=POOL_NAME] [namespace=NAMESPACE_NAME]'

    Example

    [root@mon ~]# ceph auth caps client.john mon 'allow r' osd 'allow rw pool=liverpool'
    [root@mon ~]# ceph auth caps client.paul mon 'allow rw' osd 'allow rwx pool=liverpool'
    [root@mon ~]# ceph auth caps client.brian-manager mon 'allow *' osd 'allow *'

  2. To remove a capability, you may reset the capability. If you want the user to have no access to a particular daemon that was previously set, specify an empty string:

    Example

    [root@mon ~]# ceph auth caps client.ringo mon ' ' osd ' '

Additional Resources

5.3.6. Deleting a Ceph user

You can delete a user from the Ceph storage cluster using the command-line interface.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To delete a user, use ceph auth del:

    [root@mon ~]# ceph auth del TYPE.ID

    Where TYPE is one of client, osd, mon, or mds, and ID is the user name or ID of the daemon.

5.3.8. Import Ceph user

You can import a Ceph user using the command-line interface.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To import one or more users, use ceph auth import and specify a keyring:

    ceph auth import -i /PATH/TO/KEYRING

    Example

    [root@mon ~]# ceph auth import -i /etc/ceph/ceph.keyring

Note

The Ceph storage cluster will add new users, their keys and their capabilities and will update existing users, their keys and their capabilities.

5.4. Managing Ceph keyrings

As a storage administrator, managing Ceph user keys is important for accessing the Red Hat Ceph Storage cluster. You can create keyrings, add users to keyrings, and modifying users with keyrings.

5.4.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Access to a Ceph Monitor or Ceph client node.

5.4.2. Creating a keyring

You need to provide user keys to the Ceph clients so that the Ceph client can retrieve the key for the specified user and authenticate with the Ceph Storage Cluster. Ceph Clients access keyrings to lookup a user name and retrieve the user’s key.

The ceph-authtool utility allows you to create a keyring.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To create an empty keyring, use --create-keyring or -C.

    Example

    [root@mon ~]# ceph-authtool --create-keyring /path/to/keyring

    When creating a keyring with multiple users, we recommend using the cluster name. For example, CLUSTER_NAME.keyring` for the keyring file name and saving it in the /etc/ceph/ directory so that the keyring configuration default setting will pick up the filename without requiring you to specify it in the local copy of the Ceph configuration file.

  2. Create ceph.keyring by executing the following:

    [root@mon ~]# ceph-authtool -C /etc/ceph/ceph.keyring

When creating a keyring with a single user, we recommend using the cluster name, the user type and the user name and saving it in the /etc/ceph/ directory. For example, ceph.client.admin.keyring for the client.admin user.

To create a keyring in /etc/ceph/, you must do so as root. This means the file will have rw permissions for the root user only, which is appropriate when the keyring contains administrator keys. However, if you intend to use the keyring for a particular user or group of users, ensure that you execute chown or chmod to establish appropriate keyring ownership and access.

5.4.3. Adding a user to the keyring

When you add a user to the Ceph storage cluster, you can use the get procedure to retrieve a user, key and capabilities, then save the user to a keyring file. When you only want to use one user per keyring, the Display Ceph user information procedure with the -o option will save the output in the keyring file format.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To create a keyring for the client.admin user, execute the following:

    [root@mon ~]# ceph auth get client.admin -o /etc/ceph/ceph.client.admin.keyring

    Notice that we use the recommended file format for an individual user.

  2. When you want to import users to a keyring, you can use ceph-authtool to specify the destination keyring and the source keyring.

    [root@mon ~]# ceph-authtool /etc/ceph/ceph.keyring --import-keyring /etc/ceph/ceph.client.admin.keyring

5.4.4. Creating a Ceph user with a keyring

Ceph provides the ability to create a user directly in the Red Hat Ceph Storage cluster. However, you can also create a user, keys and capabilities directly on a Ceph client keyring.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. Import a user into the keyring:

    Example

    [root@mon ~]# ceph-authtool -n client.ringo --cap osd 'allow rwx' --cap mon 'allow rwx' /etc/ceph/ceph.keyring

  2. Create a keyring and add a new user to the keyring simultaneously:

    Example:

    [root@mon ~]# ceph-authtool -C /etc/ceph/ceph.keyring -n client.ringo --cap osd 'allow rwx' --cap mon 'allow rwx' --gen-key

    In the foregoing scenarios, the new user client.ringo is only in the keyring.

  3. To add the new user to the Ceph storage cluster:

    [root@mon ~]# ceph auth add client.ringo -i /etc/ceph/ceph.keyring

Additional Resources

5.4.5. Modifying a Ceph user with a keyring

You can modify a Ceph user and their keyring using the command-line interface.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To modify the capabilities of a user record in a keyring, specify the keyring, and the user followed by the capabilities, for example:
[root@mon ~]# ceph-authtool /etc/ceph/ceph.keyring -n client.ringo --cap osd 'allow rwx' --cap mon 'allow rwx'
  1. To update the user to the Red Hat Ceph Storage cluster, you must update the user in the keyring to the user entry in the Red Hat Ceph Storage cluster:
[root@mon ~]# ceph auth import -i /etc/ceph/ceph.keyring

You may also modify user capabilities directly in the storage cluster, store the results to a keyring file; then, import the keyring into the main ceph.keyring file.

Additional Resources

  • See Import user for details on updating a Red Hat Ceph Storage cluster user from a keyring.

5.4.6. Command Line usage for Ceph users

Ceph supports the following usage for user name and secret:

--id | --user

Description
Ceph identifies users with a type and an ID. For example, TYPE.ID or client.admin, client.user1. The id, name and -n options enable you to specify the ID portion of the user name. For example, admin, user1, or foo. You can specify the user with the --id and omit the type. For example, to specify user client.foo enter the following:
[root@mon ~]# ceph --id foo --keyring /path/to/keyring health
[root@mon ~]# ceph --user foo --keyring /path/to/keyring health

--name | -n

Description
Ceph identifies users with a type and an ID. For example, TYPE.ID or client.admin, client.user1. The --name and -n options enables you to specify the fully qualified user name. You must specify the user type (typically client) with the user ID. For example:
[root@mon ~]# ceph --name client.foo --keyring /path/to/keyring health
[root@mon ~]# ceph -n client.foo --keyring /path/to/keyring health

--keyring

Description
The path to the keyring containing one or more user name and secret. The --secret option provides the same functionality, but it does not work with Ceph RADOS Gateway, which uses --secret for another purpose. You may retrieve a keyring with ceph auth get-or-create and store it locally. This is a preferred approach, because you can switch user names without switching the keyring path. For example:
[root@mon ~]# rbd map foo --pool rbd myimage --id client.foo --keyring /path/to/keyring

5.4.7. Ceph user management limitations

The cephx protocol authenticates Ceph clients and servers to each other. It is not intended to handle authentication of human users or application programs run on their behalf. If that effect is required to handle the access control needs, you must have another mechanism, which is likely to be specific to the front end used to access the Ceph object store. This other mechanism has the role of ensuring that only acceptable users and programs are able to run on the machine that Ceph will permit to access its object store.

The keys used to authenticate Ceph clients and servers are typically stored in a plain text file with appropriate permissions in a trusted host.

Important

Storing keys in plaintext files has security shortcomings, but they are difficult to avoid, given the basic authentication methods Ceph uses in the background. Those setting up Ceph systems should be aware of these shortcomings.

In particular, arbitrary user machines, especially portable machines, should not be configured to interact directly with Ceph, since that mode of use would require the storage of a plaintext authentication key on an insecure machine. Anyone who stole that machine or obtained surreptitious access to it could obtain the key that will allow them to authenticate their own machines to Ceph.

Rather than permitting potentially insecure machines to access a Ceph object store directly, users should be required to sign in to a trusted machine in the environment using a method that provides sufficient security for the purposes. That trusted machine will store the plaintext Ceph keys for the human users. A future version of Ceph may address these particular authentication issues more fully.

At the moment, none of the Ceph authentication protocols provide secrecy for messages in transit. Thus, an eavesdropper on the wire can hear and understand all data sent between clients and servers in Ceph, even if he cannot create or alter them. Those storing sensitive data in Ceph should consider encrypting their data before providing it to the Ceph system.

For example, Ceph Object Gateway provides S3 API Server-side Encryption, which encrypts unencrypted data received from a Ceph Object Gateway client before storing it in the Ceph Storage cluster and similarly decrypts data retrieved from the Ceph Storage cluster before sending it back to the client. To ensure encryption in transit between the client and the Ceph Object Gateway, the Ceph Object Gateway should be configured to use SSL.

Chapter 6. The ceph-volume utility

As a storage administrator, you can prepare, create, and activate Ceph OSDs using the ceph-volume utility. The ceph-volume utility is a single purpose command-line tool to deploy logical volumes as OSDs. It uses a plugin-type framework to deploying OSDs with different device technologies. The ceph-volume utility follows a similar workflow of the ceph-disk utility for deploying OSDs, with a predictable, and robust way of preparing, activating, and starting OSDs. Currently, the ceph-volume utility only supports the lvm plugin, with the plan to support others technologies in the future.

Important

The ceph-disk command is deprecated.

6.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

6.2. Ceph volume lvm plugin

By making use of LVM tags, the lvm sub-command is able to store and re-discover by querying devices associated with OSDs so they can be activated. This includes support for lvm-based technologies like dm-cache as well.

When using ceph-volume, the use of dm-cache is transparent, and treats dm-cache like a logical volume. The performance gains and losses when using dm-cache will depend on the specific workload. Generally, random and sequential reads will see an increase in performance at smaller block sizes. While random and sequential writes will see a decrease in performance at larger block sizes.

To use the LVM plugin, add lvm as a subcommand to the ceph-volume command:

[root@mon ~]# ceph-volume lvm

There are three subcommands to the lvm subcommand, as follows:

Note

Using the create subcommand combines the prepare and activate subcommands into one subcommand.

Additional Resources

  • See the create subcommand section for more details.

6.3. Why does ceph-volume replace ceph-disk?

Previous versions of Red Hat Ceph Storage used the ceph-disk utility to prepare, activate, and create OSDs. Starting with Red Hat Ceph Storage 4, ceph-disk is replaced by the ceph-volume utility that aims to be a single purpose command-line tool to deploy logical volumes as OSDs, while maintaining a similar API to ceph-disk when preparing, activating, and creating OSDs.

How does ceph-volume work?

The ceph-volume is a modular tool that currently supports two ways of provisioning hardware devices, legacy ceph-disk devices and LVM (Logical Volume Manager) devices. The ceph-volume lvm command uses the LVM tags to store information about devices specific to Ceph and its relationship with OSDs. It uses these tags to later re-discover and query devices associated with OSDS so that it can activate them. It supports technologies based on LVM and dm-cache as well.

The ceph-volume utility uses dm-cache transparently and treats it as a logical volume. You might consider the performance gains and losses when using dm-cache, depending on the specific workload you are handling. Generally, the performance of random and sequential read operations increases at smaller block sizes; while the performance of random and sequential write operations decreases at larger block sizes. Using ceph-volume does not introduce any significant performance penalties.

Important

The ceph-disk utility is deprecated.

Note

The ceph-volume simple command can handle legacy ceph-disk devices, if these devices are still in use.

How does ceph-disk work?

The ceph-disk utility was required to support many different types of init systems, such as upstart or sysvinit, while being able to discover devices. For this reason, ceph-disk concentrates only on GUID Partition Table (GPT) partitions. Specifically on GPT GUIDs that label devices in a unique way to answer questions like:

  • Is this device a journal?
  • Is this device an encrypted data partition?
  • Was the device left partially prepared?

To solve these questions, ceph-disk uses UDEV rules to match the GUIDs.

What are disadvantages of using ceph-disk?

Using the UDEV rules to call ceph-disk can lead to a back-and-forth between the ceph-disk systemd unit and the ceph-disk executable. The process is very unreliable and time consuming and can cause OSDs to not come up at all during the boot process of a node. Moreover, it is hard to debug, or even replicate these problems given the asynchronous behavior of UDEV.

Because ceph-disk works with GPT partitions exclusively, it cannot support other technologies, such as Logical Volume Manager (LVM) volumes, or similar device mapper devices.

To ensure the GPT partitions work correctly with the device discovery workflow, ceph-disk requires a large number of special flags to be used. In addition, these partitions require devices to be exclusively owned by Ceph.

6.4. Preparing Ceph OSDs using ceph-volume

The prepare subcommand prepares an OSD back-end object store and consumes logical volumes (LV) for both the OSD data and journal. It does not modify the logical volumes, except for adding some extra metadata tags using LVM. These tags make volumes easier to discover, and they also identify the volumes as part of the Ceph Storage Cluster and the roles of those volumes in the storage cluster.

The BlueStore OSD backend supports the following configurations:

  • A block device, a block.wal device, and a block.db device
  • A block device and a block.wal device
  • A block device and a block.db device
  • A single block device

The prepare subcommand accepts a whole device or partition, or a logical volume for block.

Prerequisites

  • Root-level access to the OSD nodes.
  • Optionally, create logical volumes. If you provide a path to a physical device, the subcommand turns the device into a logical volume. This approach is simpler, but you cannot configure or change the way the logical volume is created.

Procedure

  1. Prepare the LVM volumes:

    Syntax

    ceph-volume lvm prepare --bluestore --data VOLUME_GROUP/LOGICAL_VOLUME

    Example

    [root@osd ~]# ceph-volume lvm prepare --bluestore --data example_vg/data_lv

    1. Optionally, if you want to use a separate device for RocksDB, specify the --block.db and --block.wal options:

      Syntax

      ceph-volume lvm prepare --bluestore --block.db --block.wal --data VOLUME_GROUP/LOGICAL_VOLUME

      Example

      [root@osd ~]# ceph-volume lvm prepare --bluestore --block.db --block.wal --data example_vg/data_lv

    2. Optionally, to encrypt data, use the --dmcrypt flag:

      Syntax

      ceph-volume lvm prepare --bluestore --dmcrypt --data VOLUME_GROUP/LOGICAL_VOLUME

      Example

      [root@osd ~]# ceph-volume lvm prepare --bluestore --dmcrypt --data example_vg/data_lv

Additional Resources

6.5. Activating Ceph OSDs using ceph-volume

The activation process enables a systemd unit at boot time, which allows the correct OSD identifier and its UUID to be enabled and mounted.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD node.
  • Ceph OSDs prepared by the ceph-volume utility.

Procedure

  1. Get the OSD ID and UUID from an OSD node:

    [root@osd ~]# ceph-volume lvm list
  2. Activate the OSD:

    Syntax

    ceph-volume lvm activate --bluestore OSD_ID OSD_UUID

    Example

    [root@osd ~]# ceph-volume lvm activate --bluestore 0 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8

    To activate all OSDs that are prepared for activation, use the --all option:

    Example

    [root@osd ~]# ceph-volume lvm activate --all

Additional Resources

6.6. Creating Ceph OSDs using ceph-volume

The create subcommand calls the prepare subcommand, and then calls the activate subcommand.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD nodes.
Note

If you prefer to have more control over the creation process, you can use the prepare and activate subcommands separately to create the OSD, instead of using create. You can use the two subcommands to gradually introduce new OSDs into a storage cluster, while avoiding having to rebalance large amounts of data. Both approaches work the same way, except that using the create subcommand causes the OSD to become up and in immediately after completion.

Procedure

  1. To create a new OSD:

    Syntax

    ceph-volume lvm create --bluestore --data VOLUME_GROUP/LOGICAL_VOLUME

    Example

    [root@osd ~]# ceph-volume lvm create --bluestore --data example_vg/data_lv

Additional Resources

6.7. Using batch mode with ceph-volume

The batch subcommand automates the creation of multiple OSDs when single devices are provided.

The ceph-volume command decides the best method to use to create the OSDs, based on drive type. Ceph OSD optimization depends on the available devices:

  • If all devices are traditional hard drives, batch creates one OSD per device.
  • If all devices are solid state drives, batch creates two OSDs per device.
  • If there is a mix of traditional hard drives and solid state drives, batch uses the traditional hard drives for data, and creates the largest possible journal (block.db) on the solid state drive.
Note

The batch subcommand does not support the creation of a separate logical volume for the write-ahead-log (block.wal) device.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD nodes.

Procedure

  1. To create OSDs on several drives:

    Syntax

    ceph-volume lvm batch --bluestore PATH_TO_DEVICE [PATH_TO_DEVICE]

    Example

    [root@osd ~]# ceph-volume lvm batch --bluestore /dev/sda /dev/sdb /dev/nvme0n1

Additional Resources

Chapter 7. Ceph performance benchmark

As a storage administrator, you can benchmark performance of the Red Hat Ceph Storage cluster. The purpose of this section is to give Ceph administrators a basic understanding of Ceph’s native benchmarking tools. These tools will provide some insight into how the Ceph storage cluster is performing. This is not the definitive guide to Ceph performance benchmarking, nor is it a guide on how to tune Ceph accordingly.

7.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

7.2. Performance baseline

The OSD, including the journal, disks and the network throughput should each have a performance baseline to compare against. You can identify potential tuning opportunities by comparing the baseline performance data with the data from Ceph’s native tools. Red Hat Enterprise Linux has many built-in tools, along with a plethora of open source community tools, available to help accomplish these tasks.

Additional Resources

  • For more details about some of the available tools, see this Knowledgebase article.

7.3. Benchmarking Ceph performance

Ceph includes the rados bench command to do performance benchmarking on a RADOS storage cluster. The command will execute a write test and two types of read tests. The --no-cleanup option is important to use when testing both read and write performance. By default the rados bench command will delete the objects it has written to the storage pool. Leaving behind these objects allows the two read tests to measure sequential and random read performance.

Note

Before running these performance tests, drop all the file system caches by running the following:

[root@mon~ ]# echo 3 | sudo tee /proc/sys/vm/drop_caches && sudo sync

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. Create a new storage pool:

    [root@osd~ ]# ceph osd pool create testbench 100 100
  2. Execute a write test for 10 seconds to the newly created storage pool:

    [root@osd~ ]# rados bench -p testbench 10 write --no-cleanup

    Example Output

    Maintaining 16 concurrent writes of 4194304 bytes for up to 10 seconds or 0 objects
     Object prefix: benchmark_data_cephn1.home.network_10510
       sec Cur ops   started  finished  avg MB/s  cur MB/s  last lat   avg lat
         0       0         0         0         0         0         -         0
         1      16        16         0         0         0         -         0
         2      16        16         0         0         0         -         0
         3      16        16         0         0         0         -         0
         4      16        17         1  0.998879         1   3.19824   3.19824
         5      16        18         2   1.59849         4   4.56163   3.87993
         6      16        18         2   1.33222         0         -   3.87993
         7      16        19         3   1.71239         2   6.90712     4.889
         8      16        25         9   4.49551        24   7.75362   6.71216
         9      16        25         9   3.99636         0         -   6.71216
        10      16        27        11   4.39632         4   9.65085   7.18999
        11      16        27        11   3.99685         0         -   7.18999
        12      16        27        11   3.66397         0         -   7.18999
        13      16        28        12   3.68975   1.33333   12.8124   7.65853
        14      16        28        12   3.42617         0         -   7.65853
        15      16        28        12   3.19785         0         -   7.65853
        16      11        28        17   4.24726   6.66667   12.5302   9.27548
        17      11        28        17   3.99751         0         -   9.27548
        18      11        28        17   3.77546         0         -   9.27548
        19      11        28        17   3.57683         0         -   9.27548
     Total time run:         19.505620
    Total writes made:      28
    Write size:             4194304
    Bandwidth (MB/sec):     5.742
    
    Stddev Bandwidth:       5.4617
    Max bandwidth (MB/sec): 24
    Min bandwidth (MB/sec): 0
    Average Latency:        10.4064
    Stddev Latency:         3.80038
    Max latency:            19.503
    Min latency:            3.19824

  3. Execute a sequential read test for 10 seconds to the storage pool:

    [root@osd~ ]## rados bench -p testbench 10 seq

    Example Output

    sec Cur ops   started  finished  avg MB/s  cur MB/s  last lat   avg lat
      0       0         0         0         0         0         -         0
    Total time run:        0.804869
    Total reads made:      28
    Read size:             4194304
    Bandwidth (MB/sec):    139.153
    
    Average Latency:       0.420841
    Max latency:           0.706133
    Min latency:           0.0816332

  4. Execute a random read test for 10 seconds to the storage pool:

    [root@osd ~]# rados bench -p testbench 10 rand

    Example Output

    sec Cur ops   started  finished  avg MB/s  cur MB/s  last lat   avg lat
      0       0         0         0         0         0         -         0
      1      16        46        30   119.801       120  0.440184  0.388125
      2      16        81        65   129.408       140  0.577359  0.417461
      3      16       120       104   138.175       156  0.597435  0.409318
      4      15       157       142   141.485       152  0.683111  0.419964
      5      16       206       190   151.553       192  0.310578  0.408343
      6      16       253       237   157.608       188 0.0745175  0.387207
      7      16       287       271   154.412       136  0.792774   0.39043
      8      16       325       309   154.044       152  0.314254   0.39876
      9      16       362       346   153.245       148  0.355576  0.406032
     10      16       405       389   155.092       172   0.64734  0.398372
    Total time run:        10.302229
    Total reads made:      405
    Read size:             4194304
    Bandwidth (MB/sec):    157.248
    
    Average Latency:       0.405976
    Max latency:           1.00869
    Min latency:           0.0378431

  5. To increase the number of concurrent reads and writes, use the -t option, which the default is 16 threads. Also, the -b parameter can adjust the size of the object being written. The default object size is 4 MB. A safe maximum object size is 16 MB. Red Hat recommends running multiple copies of these benchmark tests to different pools. Doing this shows the changes in performance from multiple clients.

    Add the --run-name <label> option to control the names of the objects that get written during the benchmark test. Multiple rados bench commands may be ran simultaneously by changing the --run-name label for each running command instance. This prevents potential I/O errors that can occur when multiple clients are trying to access the same object and allows for different clients to access different objects. The --run-name option is also useful when trying to simulate a real world workload. For example:

    [root@osd ~]# rados bench -p testbench 10 write -t 4 --run-name client1

    Example Output

    Maintaining 4 concurrent writes of 4194304 bytes for up to 10 seconds or 0 objects
     Object prefix: benchmark_data_node1_12631
       sec Cur ops   started  finished  avg MB/s  cur MB/s  last lat   avg lat
         0       0         0         0         0         0         -         0
         1       4         4         0         0         0         -         0
         2       4         6         2   3.99099         4   1.94755   1.93361
         3       4         8         4   5.32498         8     2.978   2.44034
         4       4         8         4   3.99504         0         -   2.44034
         5       4        10         6   4.79504         4   2.92419    2.4629
         6       3        10         7   4.64471         4   3.02498    2.5432
         7       4        12         8   4.55287         4   3.12204   2.61555
         8       4        14        10    4.9821         8   2.55901   2.68396
         9       4        16        12   5.31621         8   2.68769   2.68081
        10       4        17        13   5.18488         4   2.11937   2.63763
        11       4        17        13   4.71431         0         -   2.63763
        12       4        18        14   4.65486         2    2.4836   2.62662
        13       4        18        14   4.29757         0         -   2.62662
    Total time run:         13.123548
    Total writes made:      18
    Write size:             4194304
    Bandwidth (MB/sec):     5.486
    
    Stddev Bandwidth:       3.0991
    Max bandwidth (MB/sec): 8
    Min bandwidth (MB/sec): 0
    Average Latency:        2.91578
    Stddev Latency:         0.956993
    Max latency:            5.72685
    Min latency:            1.91967

  6. Remove the data created by the rados bench command:

    [root@osd ~]# rados -p testbench cleanup

7.4. Benchmarking Ceph block performance

Ceph includes the rbd bench-write command to test sequential writes to the block device measuring throughput and latency. The default byte size is 4096, the default number of I/O threads is 16, and the default total number of bytes to write is 1 GB. These defaults can be modified by the --io-size, --io-threads and --io-total options respectively.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. Load the rbd kernel module, if not already loaded:

    [root@mon ~]# modprobe rbd
  2. Create a 1 GB rbd image file in the testbench pool:

    [root@mon ~]# rbd create image01 --size 1024 --pool testbench
  3. Map the image file to a device file:

    [root@mon ~]# rbd map image01 --pool testbench --name client.admin
  4. Create an ext4 file system on the block device:

    [root@mon ~]# mkfs.ext4 /dev/rbd/testbench/image01
  5. Create a new directory:

    [root@mon ~]# mkdir /mnt/ceph-block-device
  6. Mount the block device under /mnt/ceph-block-device/:

    [root@mon ~]# mount /dev/rbd/testbench/image01 /mnt/ceph-block-device
  7. Execute the write performance test against the block device

    [root@mon ~]# rbd bench --io-type write image01 --pool=testbench

    Example

    bench-write  io_size 4096 io_threads 16 bytes 1073741824 pattern seq
      SEC       OPS   OPS/SEC   BYTES/SEC
        2     11127   5479.59  22444382.79
        3     11692   3901.91  15982220.33
        4     12372   2953.34  12096895.42
        5     12580   2300.05  9421008.60
        6     13141   2101.80  8608975.15
        7     13195    356.07  1458459.94
        8     13820    390.35  1598876.60
        9     14124    325.46  1333066.62
        ..

Additional Resources

  • See the Block Device Commands section in the Red Hat Ceph Storage Block Device Guide for more information on the rbd command.

Chapter 8. Ceph performance counters

As a storage administrator, you can gather performance metrics of the Red Hat Ceph Storage cluster. The Ceph performance counters are a collection of internal infrastructure metrics. The collection, aggregation, and graphing of this metric data can be done by an assortment of tools and can be useful for performance analytics.

8.1. Prerequisites

  • A running Red Hat Ceph Storage cluster.

8.2. Access to Ceph performance counters

The performance counters are available through a socket interface for the Ceph Monitors and the OSDs. The socket file for each respective daemon is located under /var/run/ceph, by default. The performance counters are grouped together into collection names. These collections names represent a subsystem or an instance of a subsystem.

Here is the full list of the Monitor and the OSD collection name categories with a brief description for each :

Monitor Collection Name Categories

  • Cluster Metrics - Displays information about the storage cluster: Monitors, OSDs, Pools, and PGs
  • Level Database Metrics - Displays information about the back-end KeyValueStore database
  • Monitor Metrics - Displays general monitor information
  • Paxos Metrics - Displays information on cluster quorum management
  • Throttle Metrics - Displays the statistics on how the monitor is throttling

OSD Collection Name Categories

  • Write Back Throttle Metrics - Displays the statistics on how the write back throttle is tracking unflushed IO
  • Level Database Metrics - Displays information about the back-end KeyValueStore database
  • Objecter Metrics - Displays information on various object-based operations
  • Read and Write Operations Metrics - Displays information on various read and write operations
  • Recovery State Metrics - Displays - Displays latencies on various recovery states
  • OSD Throttle Metrics - Display the statistics on how the OSD is throttling

RADOS Gateway Collection Name Categories

  • Object Gateway Client Metrics - Displays statistics on GET and PUT requests
  • Objecter Metrics - Displays information on various object-based operations
  • Object Gateway Throttle Metrics - Display the statistics on how the OSD is throttling

8.3. Display the Ceph performance counters

The ceph daemon .. perf schema command outputs the available metrics. Each metric has an associated bit field value type.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To view the metric’s schema:

    ceph daemon DAEMON_NAME perf schema
    Note

    You must run the ceph daemon command from the node running the daemon.

  2. Executing ceph daemon .. perf schema command from the Monitor node:

    [root@mon ~]# ceph daemon mon.`hostname -s` perf schema

    Example

    {
        "cluster": {
            "num_mon": {
                "type": 2
            },
            "num_mon_quorum": {
                "type": 2
            },
            "num_osd": {
                "type": 2
            },
            "num_osd_up": {
                "type": 2
            },
            "num_osd_in": {
                "type": 2
            },
    ...

  3. Executing the ceph daemon .. perf schema command from the OSD node:

    [root@mon ~]# ceph daemon osd.0 perf schema

    Example

    ...
    "filestore": {
            "journal_queue_max_ops": {
                "type": 2
            },
            "journal_queue_ops": {
                "type": 2
            },
            "journal_ops": {
                "type": 10
            },
            "journal_queue_max_bytes": {
                "type": 2
            },
            "journal_queue_bytes": {
                "type": 2
            },
            "journal_bytes": {
                "type": 10
            },
            "journal_latency": {
                "type": 5
            },
    ...

Table 8.1. The bit field value definitions

BitMeaning

1

Floating point value

2

Unsigned 64-bit integer value

4

Average (Sum + Count)

8

Counter

Each value will have bit 1 or 2 set to indicate the type, either a floating point or an integer value. When bit 4 is set, there will be two values to read, a sum and a count. When bit 8 is set, the average for the previous interval would be the sum delta, since the previous read, divided by the count delta. Alternatively, dividing the values outright would provide the lifetime average value. Typically these are used to measure latencies, the number of requests and a sum of request latencies. Some bit values are combined, for example 5, 6 and 10. A bit value of 5 is a combination of bit 1 and bit 4. This means the average will be a floating point value. A bit value of 6 is a combination of bit 2 and bit 4. This means the average value will be an integer. A bit value of 10 is a combination of bit 2 and bit 8. This means the counter value will be an integer value.

Additional Resources

8.4. Dump the Ceph performance counters

The ceph daemon .. perf dump command outputs the current values and groups the metrics under the collection name for each subsystem.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. To view the current metric data:

    # ceph daemon DAEMON_NAME perf dump
    Note

    You must run the ceph daemon command from the node running the daemon.

  2. Executing ceph daemon .. perf dump command from the Monitor node:

    # ceph daemon mon.`hostname -s` perf dump

    Example

    {
        "cluster": {
            "num_mon": 1,
            "num_mon_quorum": 1,
            "num_osd": 2,
            "num_osd_up": 2,
            "num_osd_in": 2,
    ...

  3. Executing the ceph daemon .. perf dump command from the OSD node:

    # ceph daemon osd.0 perf dump

    Example

    ...
    "filestore": {
            "journal_queue_max_ops": 300,
            "journal_queue_ops": 0,
            "journal_ops": 992,
            "journal_queue_max_bytes": 33554432,
            "journal_queue_bytes": 0,
            "journal_bytes": 934537,
            "journal_latency": {
                "avgcount": 992,
                "sum": 254.975925772
            },
    ...

Additional Resources

8.5. Average count and sum

All latency numbers have a bit field value of 5. This field contains floating point values for the average count and sum. The avgcount is the number of operations within this range and the sum is the total latency in seconds. When dividing the sum by the avgcount this will provide you with an idea of the latency per operation.

Additional Resources

  • To view a short description of each OSD metric available, please see the Ceph OSD table.

8.6. Ceph Monitor metrics

Table 8.2. Cluster Metrics Table

Collection NameMetric NameBit Field ValueShort Description

cluster

num_mon

2

Number of monitors

 

num_mon_quorum

2

Number of monitors in quorum

 

num_osd

2

Total number of OSD

 

num_osd_up

2

Number of OSDs that are up

 

num_osd_in

2

Number of OSDs that are in cluster

 

osd_epoch

2

Current epoch of OSD map

 

osd_bytes

2

Total capacity of cluster in bytes

 

osd_bytes_used

2

Number of used bytes on cluster

 

osd_bytes_avail

2

Number of available bytes on cluster

 

num_pool

2

Number of pools

 

num_pg

2

Total number of placement groups

 

num_pg_active_clean

2

Number of placement groups in active+clean state

 

num_pg_active

2

Number of placement groups in active state

 

num_pg_peering

2

Number of placement groups in peering state

 

num_object

2

Total number of objects on cluster

 

num_object_degraded

2

Number of degraded (missing replicas) objects

 

num_object_misplaced

2

Number of misplaced (wrong location in the cluster) objects

 

num_object_unfound

2

Number of unfound objects

 

num_bytes

2

Total number of bytes of all objects

 

num_mds_up

2

Number of MDSs that are up

 

num_mds_in

2

Number of MDS that are in cluster

 

num_mds_failed

2

Number of failed MDS

 

mds_epoch

2

Current epoch of MDS map

Table 8.3. Level Database Metrics Table

Collection NameMetric NameBit Field ValueShort Description

leveldb

leveldb_get

10

Gets

 

leveldb_transaction

10

Transactions

 

leveldb_compact

10

Compactions

 

leveldb_compact_range

10

Compactions by range

 

leveldb_compact_queue_merge

10

Mergings of ranges in compaction queue

 

leveldb_compact_queue_len

2

Length of compaction queue

Table 8.4. General Monitor Metrics Table

Collection NameMetric NameBit Field ValueShort Description

mon

num_sessions

2

Current number of opened monitor sessions

 

session_add

10

Number of created monitor sessions

 

session_rm

10

Number of remove_session calls in monitor

 

session_trim

10

Number of trimed monitor sessions

 

num_elections

10

Number of elections monitor took part in

 

election_call

10

Number of elections started by monitor

 

election_win

10

Number of elections won by monitor

 

election_lose

10

Number of elections lost by monitor

Table 8.5. Paxos Metrics Table

Collection NameMetric NameBit Field ValueShort Description

paxos

start_leader

10

Starts in leader role

 

start_peon

10

Starts in peon role

 

restart

10

Restarts

 

refresh

10

Refreshes

 

refresh_latency

5

Refresh latency

 

begin

10

Started and handled begins

 

begin_keys

6

Keys in transaction on begin

 

begin_bytes

6

Data in transaction on begin

 

begin_latency

5

Latency of begin operation

 

commit

10

Commits

 

commit_keys

6

Keys in transaction on commit

 

commit_bytes

6

Data in transaction on commit

 

commit_latency

5

Commit latency

 

collect

10

Peon collects

 

collect_keys

6

Keys in transaction on peon collect

 

collect_bytes

6

Data in transaction on peon collect

 

collect_latency

5

Peon collect latency

 

collect_uncommitted

10

Uncommitted values in started and handled collects

 

collect_timeout

10

Collect timeouts

 

accept_timeout

10

Accept timeouts

 

lease_ack_timeout

10

Lease acknowledgement timeouts

 

lease_timeout

10

Lease timeouts

 

store_state

10

Store a shared state on disk

 

store_state_keys

6

Keys in transaction in stored state

 

store_state_bytes

6

Data in transaction in stored state

 

store_state_latency

5

Storing state latency

 

share_state

10

Sharings of state

 

share_state_keys

6

Keys in shared state

 

share_state_bytes

6

Data in shared state

 

new_pn

10

New proposal number queries

 

new_pn_latency

5

New proposal number getting latency

Table 8.6. Throttle Metrics Table

Collection NameMetric NameBit Field ValueShort Description

throttle-*

val

10

Currently available throttle

 

max

10

Max value for throttle

 

get

10

Gets

 

get_sum

10

Got data

 

get_or_fail_fail

10

Get blocked during get_or_fail

 

get_or_fail_success

10

Successful get during get_or_fail

 

take

10

Takes

 

take_sum

10

Taken data

 

put

10

Puts

 

put_sum

10

Put data

 

wait

5

Waiting latency

8.7. Ceph OSD metrics

Table 8.7. Write Back Throttle Metrics Table

Collection NameMetric NameBit Field ValueShort Description

WBThrottle

bytes_dirtied

2

Dirty data

 

bytes_wb

2

Written data

 

ios_dirtied

2

Dirty operations

 

ios_wb

2

Written operations

 

inodes_dirtied

2

Entries waiting for write

 

inodes_wb

2

Written entries

Table 8.8. Level Database Metrics Table

Collection NameMetric NameBit Field ValueShort Description

leveldb

leveldb_get

10

Gets

 

leveldb_transaction

10

Transactions

 

leveldb_compact

10

Compactions

 

leveldb_compact_range

10

Compactions by range

 

leveldb_compact_queue_merge

10

Mergings of ranges in compaction queue

 

leveldb_compact_queue_len

2

Length of compaction queue

Table 8.9. Objecter Metrics Table

Collection NameMetric NameBit Field ValueShort Description

objecter

op_active

2

Active operations

 

op_laggy

2

Laggy operations

 

op_send

10

Sent operations

 

op_send_bytes

10

Sent data

 

op_resend

10

Resent operations

 

op_ack

10

Commit callbacks

 

op_commit

10

Operation commits

 

op

10

Operation

 

op_r

10

Read operations

 

op_w

10

Write operations

 

op_rmw

10

Read-modify-write operations

 

op_pg

10

PG operation

 

osdop_stat

10

Stat operations

 

osdop_create

10

Create object operations

 

osdop_read

10

Read operations

 

osdop_write

10

Write operations

 

osdop_writefull

10

Write full object operations

 

osdop_append

10

Append operation

 

osdop_zero

10

Set object to zero operations

 

osdop_truncate

10

Truncate object operations

 

osdop_delete

10

Delete object operations

 

osdop_mapext

10

Map extent operations

 

osdop_sparse_read

10

Sparse read operations

 

osdop_clonerange

10

Clone range operations

 

osdop_getxattr

10

Get xattr operations

 

osdop_setxattr

10

Set xattr operations

 

osdop_cmpxattr

10

Xattr comparison operations

 

osdop_rmxattr

10

Remove xattr operations

 

osdop_resetxattrs

10

Reset xattr operations

 

osdop_tmap_up

10

TMAP update operations

 

osdop_tmap_put

10

TMAP put operations

 

osdop_tmap_get

10

TMAP get operations

 

osdop_call

10

Call (execute) operations

 

osdop_watch

10

Watch by object operations

 

osdop_notify

10

Notify about object operations

 

osdop_src_cmpxattr

10

Extended attribute comparison in multi operations

 

osdop_other

10

Other operations

 

linger_active

2

Active lingering operations

 

linger_send

10

Sent lingering operations

 

linger_resend

10

Resent lingering operations

 

linger_ping

10

Sent pings to lingering operations

 

poolop_active

2

Active pool operations

 

poolop_send

10

Sent pool operations

 

poolop_resend

10

Resent pool operations

 

poolstat_active

2

Active get pool stat operations

 

poolstat_send

10

Pool stat operations sent

 

poolstat_resend

10

Resent pool stats

 

statfs_active

2

Statfs operations

 

statfs_send

10

Sent FS stats

 

statfs_resend

10

Resent FS stats

 

command_active

2

Active commands

 

command_send

10

Sent commands

 

command_resend

10

Resent commands

 

map_epoch

2

OSD map epoch

 

map_full

10

Full OSD maps received

 

map_inc

10

Incremental OSD maps received

 

osd_sessions

2

Open sessions

 

osd_session_open

10

Sessions opened

 

osd_session_close

10

Sessions closed

 

osd_laggy

2

Laggy OSD sessions

Table 8.10. Read and Write Operations Metrics Table

Collection NameMetric NameBit Field ValueShort Description

osd

op_wip

2

Replication operations currently being processed (primary)

 

op_in_bytes

10

Client operations total write size

 

op_out_bytes

10

Client operations total read size

 

op_latency

5

Latency of client operations (including queue time)

 

op_process_latency

5

Latency of client operations (excluding queue time)

 

op_r

10

Client read operations

 

op_r_out_bytes

10

Client data read

 

op_r_latency

5

Latency of read operation (including queue time)

 

op_r_process_latency

5

Latency of read operation (excluding queue time)

 

op_w

10

Client write operations

 

op_w_in_bytes

10

Client data written

 

op_w_rlat

5

Client write operation readable/applied latency

 

op_w_latency

5

Latency of write operation (including queue time)

 

op_w_process_latency

5

Latency of write operation (excluding queue time)

 

op_rw

10

Client read-modify-write operations

 

op_rw_in_bytes

10

Client read-modify-write operations write in

 

op_rw_out_bytes

10

Client read-modify-write operations read out

 

op_rw_rlat

5

Client read-modify-write operation readable/applied latency

 

op_rw_latency

5

Latency of read-modify-write operation (including queue time)

 

op_rw_process_latency

5

Latency of read-modify-write operation (excluding queue time)

 

subop

10

Suboperations

 

subop_in_bytes

10

Suboperations total size

 

subop_latency

5

Suboperations latency

 

subop_w

10

Replicated writes

 

subop_w_in_bytes

10

Replicated written data size

 

subop_w_latency

5

Replicated writes latency

 

subop_pull

10

Suboperations pull requests

 

subop_pull_latency

5

Suboperations pull latency

 

subop_push

10

Suboperations push messages

 

subop_push_in_bytes

10

Suboperations pushed size

 

subop_push_latency

5

Suboperations push latency

 

pull

10

Pull requests sent

 

push

10

Push messages sent

 

push_out_bytes

10

Pushed size

 

push_in

10

Inbound push messages

 

push_in_bytes

10

Inbound pushed size

 

recovery_ops

10

Started recovery operations

 

loadavg

2

CPU load

 

buffer_bytes

2

Total allocated buffer size

 

numpg

2

Placement groups

 

numpg_primary

2

Placement groups for which this osd is primary

 

numpg_replica

2

Placement groups for which this osd is replica

 

numpg_stray

2

Placement groups ready to be deleted from this osd

 

heartbeat_to_peers

2

Heartbeat (ping) peers we send to

 

heartbeat_from_peers

2

Heartbeat (ping) peers we recv from

 

map_messages

10

OSD map messages

 

map_message_epochs

10

OSD map epochs

 

map_message_epoch_dups

10

OSD map duplicates

 

stat_bytes

2

OSD size

 

stat_bytes_used

2

Used space

 

stat_bytes_avail

2

Available space

 

copyfrom

10

Rados 'copy-from' operations

 

tier_promote

10

Tier promotions

 

tier_flush

10

Tier flushes

 

tier_flush_fail

10

Failed tier flushes

 

tier_try_flush

10

Tier flush attempts

 

tier_try_flush_fail

10

Failed tier flush attempts

 

tier_evict

10

Tier evictions

 

tier_whiteout

10

Tier whiteouts

 

tier_dirty

10

Dirty tier flag set

 

tier_clean

10

Dirty tier flag cleaned

 

tier_delay

10

Tier delays (agent waiting)

 

tier_proxy_read

10

Tier proxy reads

 

agent_wake

10

Tiering agent wake up

 

agent_skip

10

Objects skipped by agent

 

agent_flush

10

Tiering agent flushes

 

agent_evict

10

Tiering agent evictions

 

object_ctx_cache_hit

10

Object context cache hits

 

object_ctx_cache_total

10

Object context cache lookups

Table 8.11. Recovery State Metrics Table

Collection NameMetric NameBit Field ValueShort Description

recoverystate_perf

initial_latency

5

Initial recovery state latency

 

started_latency

5

Started recovery state latency

 

reset_latency

5

Reset recovery state latency

 

start_latency

5

Start recovery state latency

 

primary_latency

5

Primary recovery state latency

 

peering_latency

5

Peering recovery state latency

 

backfilling_latency

5

Backfilling recovery state latency

 

waitremotebackfillreserved_latency

5

Wait remote backfill reserved recovery state latency

 

waitlocalbackfillreserved_latency

5

Wait local backfill reserved recovery state latency

 

notbackfilling_latency

5

Notbackfilling recovery state latency

 

repnotrecovering_latency

5

Repnotrecovering recovery state latency

 

repwaitrecoveryreserved_latency

5

Rep wait recovery reserved recovery state latency

 

repwaitbackfillreserved_latency

5

Rep wait backfill reserved recovery state latency

 

RepRecovering_latency

5

RepRecovering recovery state latency

 

activating_latency

5

Activating recovery state latency

 

waitlocalrecoveryreserved_latency

5

Wait local recovery reserved recovery state latency

 

waitremoterecoveryreserved_latency

5

Wait remote recovery reserved recovery state latency

 

recovering_latency

5

Recovering recovery state latency

 

recovered_latency

5

Recovered recovery state latency

 

clean_latency

5

Clean recovery state latency

 

active_latency

5

Active recovery state latency

 

replicaactive_latency

5

Replicaactive recovery state latency

 

stray_latency

5

Stray recovery state latency

 

getinfo_latency

5

Getinfo recovery state latency

 

getlog_latency

5

Getlog recovery state latency

 

waitactingchange_latency

5

Waitactingchange recovery state latency

 

incomplete_latency

5

Incomplete recovery state latency

 

getmissing_latency

5

Getmissing recovery state latency

 

waitupthru_latency

5

Waitupthru recovery state latency

Table 8.12. OSD Throttle Metrics Table

Collection NameMetric NameBit Field ValueShort Description

throttle-*

val

10

Currently available throttle

 

max

10

Max value for throttle

 

get

10

Gets

 

get_sum

10

Got data

 

get_or_fail_fail

10

Get blocked during get_or_fail

 

get_or_fail_success

10

Successful get during get_or_fail

 

take

10

Takes

 

take_sum

10

Taken data

 

put

10

Puts

 

put_sum

10

Put data

 

wait

5

Waiting latency

8.8. Ceph Object Gateway metrics

Table 8.13. RADOS Client Metrics Table

Collection NameMetric NameBit Field ValueShort Description

client.rgw.<rgw_node_name>

req

10

Requests

 

failed_req

10

Aborted requests

 

get

10

Gets

 

get_b

10

Size of gets

 

get_initial_lat

5

Get latency

 

put

10

Puts

 

put_b

10

Size of puts

 

put_initial_lat

5

Put latency

 

qlen

2

Queue length

 

qactive

2

Active requests queue

 

cache_hit

10

Cache hits

 

cache_miss

10

Cache miss

 

keystone_token_cache_hit

10

Keystone token cache hits

 

keystone_token_cache_miss

10

Keystone token cache miss

Table 8.14. Objecter Metrics Table

Collection NameMetric NameBit Field ValueShort Description

objecter

op_active

2

Active operations

 

op_laggy

2

Laggy operations

 

op_send

10

Sent operations

 

op_send_bytes

10

Sent data

 

op_resend

10

Resent operations

 

op_ack

10

Commit callbacks

 

op_commit

10

Operation commits

 

op

10

Operation

 

op_r

10

Read operations

 

op_w

10

Write operations

 

op_rmw

10

Read-modify-write operations

 

op_pg

10

PG operation

 

osdop_stat

10

Stat operations

 

osdop_create

10

Create object operations

 

osdop_read

10

Read operations

 

osdop_write

10

Write operations

 

osdop_writefull

10

Write full object operations

 

osdop_append

10

Append operation

 

osdop_zero

10

Set object to zero operations

 

osdop_truncate

10

Truncate object operations

 

osdop_delete

10

Delete object operations

 

osdop_mapext

10

Map extent operations

 

osdop_sparse_read

10

Sparse read operations

 

osdop_clonerange

10

Clone range operations

 

osdop_getxattr

10

Get xattr operations

 

osdop_setxattr

10

Set xattr operations

 

osdop_cmpxattr

10

Xattr comparison operations

 

osdop_rmxattr

10

Remove xattr operations

 

osdop_resetxattrs

10

Reset xattr operations

 

osdop_tmap_up

10

TMAP update operations

 

osdop_tmap_put

10

TMAP put operations

 

osdop_tmap_get

10

TMAP get operations

 

osdop_call

10

Call (execute) operations

 

osdop_watch

10

Watch by object operations

 

osdop_notify

10

Notify about object operations

 

osdop_src_cmpxattr

10

Extended attribute comparison in multi operations

 

osdop_other

10

Other operations

 

linger_active

2

Active lingering operations

 

linger_send

10

Sent lingering operations

 

linger_resend

10

Resent lingering operations

 

linger_ping

10

Sent pings to lingering operations

 

poolop_active

2

Active pool operations

 

poolop_send

10

Sent pool operations

 

poolop_resend

10

Resent pool operations

 

poolstat_active

2

Active get pool stat operations

 

poolstat_send

10

Pool stat operations sent

 

poolstat_resend

10

Resent pool stats

 

statfs_active

2

Statfs operations

 

statfs_send

10

Sent FS stats

 

statfs_resend

10

Resent FS stats

 

command_active

2

Active commands

 

command_send

10

Sent commands

 

command_resend

10

Resent commands

 

map_epoch

2

OSD map epoch

 

map_full

10

Full OSD maps received

 

map_inc

10

Incremental OSD maps received

 

osd_sessions

2

Open sessions

 

osd_session_open

10

Sessions opened

 

osd_session_close

10

Sessions closed

 

osd_laggy

2

Laggy OSD sessions

Table 8.15. RADOS Gateway Throttle Metrics Table

Collection NameMetric NameBit Field ValueShort Description

throttle-*

val

10

Currently available throttle

 

max

10

Max value for throttle

 

get

10

Gets

 

get_sum

10

Got data

 

get_or_fail_fail

10

Get blocked during get_or_fail

 

get_or_fail_success

10

Successful get during get_or_fail

 

take

10

Takes

 

take_sum

10

Taken data

 

put

10

Puts

 

put_sum

10

Put data

 

wait

5

Waiting latency

Chapter 9. BlueStore

Starting with Red Hat Ceph Storage 4, BlueStore is the default object store for the OSD daemons. The earlier object store, FileStore, requires a file system on top of raw block devices. Objects are then written to the file system. BlueStore does not require an initial file system, because BlueStore puts objects directly on the block device.

Important

BlueStore provides a high-performance backend for OSD daemons in a production environment. By default, BlueStore is configured to be self-tuning. If you determine that your environment performs better with BlueStore tuned manually, please contact Red Hat support and share the details of your configuration to help us improve the auto-tuning capability. Red Hat looks forward to your feedback and appreciates your recommendations.

9.1. Ceph BlueStore

The following are some of the main features of using BlueStore:

Direct management of storage devices
BlueStore consumes raw block devices or partitions. This avoids any intervening layers of abstraction, such as local file systems like XFS, that might limit performance or add complexity.
Metadata management with RocksDB
BlueStore uses the RocksDB’ key-value database to manage internal metadata, such as the mapping from object names to block locations on a disk.
Full data and metadata checksumming
By default all data and metadata written to BlueStore is protected by one or more checksums. No data or metadata are read from disk or returned to the user without verification.
Efficient copy-on-write
The Ceph Block Device and Ceph File System snapshots rely on a copy-on-write clone mechanism that is implemented efficiently in BlueStore. This results in efficient I/O both for regular snapshots and for erasure coded pools which rely on cloning to implement efficient two-phase commits.
No large double-writes
BlueStore first writes any new data to unallocated space on a block device, and then commits a RocksDB transaction that updates the object metadata to reference the new region of the disk. Only when the write operation is below a configurable size threshold, it falls back to a write-ahead journaling scheme, similar to how FileStore operates.
Multi-device support

BlueStore can use multiple block devices for storing different data. For example: Hard Disk Drive (HDD) for the data, Solid-state Drive (SSD) for metadata, Non-volatile Memory (NVM) or Non-volatile random-access memory (NVRAM) or persistent memory for the RocksDB write-ahead log (WAL). See Ceph BlueStore devices for details.

Note

The ceph-disk utility does not yet provision multiple devices. To use multiple devices, OSDs must be set up manually.

Efficient block device usage
Because BlueStore does not use any file system, it minimizes the need to clear the storage device cache.

9.2. Ceph BlueStore devices

This section explains what block devices the BlueStore back end uses.

BlueStore manages either one, two, or three storage devices.

  • Primary
  • WAL
  • DB

In the simplest case, BlueStore consumes a single (primary) storage device. The storage device is partitioned into two parts that contain:

  • OSD metadata: A small partition formatted with XFS that contains basic metadata for the OSD. This data directory includes information about the OSD, such as its identifier, which cluster it belongs to, and its private keyring.
  • Data: A large partition occupying the rest of the device that is managed directly by BlueStore and that contains all of the OSD data. This primary device is identified by a block symbolic link in the data directory.

You can also use two additional devices:

  • A WAL (write-ahead-log) device: A device that stores BlueStore internal journal or write-ahead log. It is identified by the block.wal symbolic link in the data directory. Consider using a WAL device only if the device is faster than the primary device. For example, when the WAL device uses an SSD disk and the primary devices uses an HDD disk.
  • A DB device: A device that stores BlueStore internal metadata. The embedded RocksDB database puts as much metadata as it can on the DB device instead of on the primary device to improve performance. If the DB device is full, it starts adding metadata to the primary device. Consider using a DB device only if the device is faster than the primary device.
Warning

If you have only a less than a gigabyte storage available on fast devices. Red Hat recommends using it as a WAL device. If you have more fast devices available, consider using it as a DB device. The BlueStore journal is always placed on the fastest device, so using a DB device provides the same benefit that the WAL device while also allows for storing additional metadata.

9.3. Ceph BlueStore caching

The BlueStore cache is a collection of buffers that, depending on configuration, can be populated with data as the OSD daemon does reading from or writing to the disk. By default in Red Hat Ceph Storage, BlueStore will cache on reads, but not writes. This is because the bluestore_default_buffered_write option is set to false to avoid potential overhead associated with cache eviction.

If the bluestore_default_buffered_write option is set to true, data is written to the buffer first, and then committed to disk. Afterwards, a write acknowledgement is sent to the client, allowing subsequent reads faster access to the data already in cache, until that data is evicted.

Read-heavy workloads will not see an immediate benefit from BlueStore caching. As more reading is done, the cache will grow over time and subsequent reads will see an improvement in performance. How fast the cache populates depends on the BlueStore block and database disk type, and the client’s workload requirements.

Important

Please contact Red Hat support before enabling the bluestore_default_buffered_write option.

9.4. Sizing considerations for Ceph BlueStore

When mixing traditional and solid state drives using BlueStore OSDs, it is important to size the RocksDB logical volume (block.db) appropriately. Red Hat recommends that the RocksDB logical volume be no less than 4% of the block size with object, file and mixed workloads. Red Hat supports 1% of the BlueStore block size with RocksDB and OpenStack block workloads. For example, if the block size is 1 TB for an object workload, then at a minimum, create a 40 GB RocksDB logical volume.

When not mixing drive types, there is no requirement to have a separate RocksDB logical volume. BlueStore will automatically manage the sizing of RocksDB.

BlueStore’s cache memory is used for the key-value pair metadata for RocksDB, BlueStore metadata and object data.

Note

The BlueStore cache memory values are in addition to the memory footprint already being consumed by the OSD.

9.5. Adding Ceph BlueStore OSDs

This section describes how to install a new Ceph OSD node with the BlueStore back end object store.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the node.

Procedure

  1. Add a new OSD node to the [osds] section in Ansible inventory file, by default located at /etc/ansible/hosts.

    [osds]
    node1
    node2
    node3
    HOST_NAME

    Replace:

    • HOST_NAME with the name of the OSD node

    Example

    [osds]
    node1
    node2
    node3
    node4

  2. Navigate to the /usr/share/ceph-ansible/ directory.

    [user@admin ~]$ cd /usr/share/ceph-ansible
  3. Create the host_vars directory.

    [root@admin ceph-ansible] mkdir host_vars
  4. Create the configuration file for the newly added OSD in host_vars.

    [root@admin ceph-ansible] touch host_vars/HOST_NAME.yml

    Replace:

    • HOST_NAME with the host name of the newly added OSD

    Example

    [root@admin ceph-ansible] touch host_vars/node4.yml

  5. Add the following setting to the newly created file:

    osd_objectstore: bluestore
    Note

    To use BlueStore for all OSDs, add osd_objectstore:bluestore to the group_vars/all.yml file.

  6. Configure the BlueStore OSDs, in host_vars/HOST_NAME.yml:

    lvm_volumes:
      - data: DATALV
        data_vg: DATAVG

    Replace:

    • DATALV with the data logical volume name
    • DATAVG with the data logical volume group name

    Example

    lvm_volumes:
      - data: data-lv1
        data_vg: vg1

  7. Optional. If you want to store the block.wal and block.db on dedicated logical volumes, edit the host_vars/HOST_NAME.yml file as follows:

    lvm_volumes:
      - data: DATALV
        wal: WALLV
        wal_vg: VG
        db: DBLV
        db_vg: VG

    Replace:

    • DATALV with the logical volume where the data should be contained
    • WALLV with the logical volume where the write-ahead-log should be contained
    • VG with the volume group the WAL and/or DB device LVs are on
    • DBLV with the logical volume the BlueStore internal metadata should be contained

    Example

    lvm_volumes:
      - data: data-lv3
        wal: wal-lv1
        wal_vg: vg3
        db: db-lv3
        db_vg: vg3

    Note

    When using lvm_volumes: with osd_objectstore: bluestore the lvm_volumes YAML dictionary must contain at least data. When defining wal or db, it must have both the LV name and VG name (db and wal are not required). This allows for four combinations: just data, data and wal, data and wal and db, or data and db. Data can be a raw device, lv or partition. The wal and db can be a lv or partition. When specifying a raw device or partition ceph-volume will put logical volumes on top of them.

    Note

    Currently, ceph-ansible does not create the volume groups or the logical volumes. This must be done before running the Anisble playbook.

  8. Open and edit the group_vars/all.yml file, and uncomment the osd_memory_target option. Adjust the value on how much memory you want the OSD to consume.

    Note

    The default value for the osd_memory_target option is 4000000000, which is 4 GB. This option pins the BlueStore cache in memory.

    Important

    The osd_memory_target option only applies to BlueStore-backed OSDs.

  9. Run the following Ansible playbook:

    [user@admin ceph-ansible]$ ansible-playbook site.yml
  10. From a Ceph Monitor node, verify that the new OSD has been successfully added:

    [root@mon ~]# ceph osd tree

9.6. Tuning Ceph BlueStore for small writes

In BlueStore, the raw partition is allocated and managed in chunks of bluestore_min_alloc_size. By default, bluestore_min_alloc_size is 64 KB for HDDs, and 16 KB for SSDs. The unwritten area in each chunk is filled with zeroes when it is written to the raw partition. This can lead to wasted unused space when not properly sized for your workload, for example when writing small objects.

It is best practice to set bluestore_min_alloc_size to match the smallest write so this can write amplification penalty can be avoided.

For example, if your client writes 4 KB objects frequently, use ceph-ansible to configure the following setting on OSD nodes:

bluestore_min_alloc_size = 4096

Note

The settings bluestore_min_alloc_size_ssd and bluestore_min_alloc_size_hdd are specific to SSDs and HDDs, respectively, but setting them is not necessary because setting bluestore_min_alloc_size overrides them.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • New servers that can be freshly provisioned as OSD nodes, or:
  • OSD nodes that can be redeployed.

Procedure

  1. Optional: If redeploying an existing OSD node, use the shrink-osd.yml Ansible playbook to remove the OSD from the cluster.

    ansible-playbook -v infrastructure-playbooks/shrink-osd.yml -e osd_to_kill=OSD_ID

    Example

    [admin@admin ceph-ansible]$ ansible-playbook -v infrastructure-playbooks/shrink-osd.yml -e osd_to_kill=1

  2. If redeploying an existing OSD node, wipe the OSD drives and reinstall the OS.
  3. Prepare the node for OSD provisioning using Ansible. Such as, enabling Red Hat Ceph Storage repositories, adding an Ansible user, and enabling password-less SSH login.
  4. Add the bluestore_min_alloc_size to the ceph_conf_overrides section of the group_vars/all.yml Ansible playbook:

    ceph_conf_overrides:
      osd:
        bluestore_min_alloc_size: 4096
  5. If deploying a new node, add it to the Ansible inventory file, normally /etc/ansible/hosts:

    [osds]
    OSD_NODE_NAME

    Example

    [osds]
    osd1 devices="[ '/dev/sdb' ]"

  6. Provision the OSD node using Ansible:

    ansible-playbook -v site.yml -l OSD_NODE_NAME

    Example

    [admin@admin ceph-ansible]$ ansible-playbook -v site.yml -l osd1

  7. After the playbook finishes, verify the setting using the ceph daemon command:

    ceph daemon OSD.ID config get bluestore_min_alloc_size

    Example

    [root@osd1 ~]# ceph daemon osd.1 config get bluestore_min_alloc_size
    {
        "bluestore_min_alloc_size": "4096"
    }

    You can see bluestore_min_alloc_size is set to 4096 bytes, which is equivalent to 4 KiB.

Additional Resources

9.7. The BlueStore fragmentation tool

As a storage administrator, you will want to periodically check the fragmentation level of your BlueStore OSDs. You can check fragmentation levels with one simple command for offline or online OSDs.

9.7.1. Prerequisites

  • A running Red Hat Ceph Storage 3.3 or higher storage cluster.
  • BlueStore OSDs.

9.7.2. What is the BlueStore fragmentation tool?

For BlueStore OSDs, the free space gets fragmented over time on the underlying storage device. Some fragmentation is normal, but when there is excessive fragmentation this causes poor performance.

The BlueStore fragmentation tool generates a score on the fragmentation level of the BlueStore OSD. This fragmentation score is given as a range, 0 through 1. A score of 0 means no fragmentation, and a score of 1 means severe fragmentation.

Table 9.1. Fragmentation scores' meaning

ScoreFragmentation Amount

0.0 - 0.4

None to tiny fragmentation.

0.4 - 0.7

Small and acceptable fragmentation.

0.7 - 0.9

Considerable, but safe fragmentation.

0.9 - 1.0

Severe fragmentation and that causes performance issues.

Important

If you have severe fragmentation, and need some help in resolving the issue, contact Red Hat Support.

9.7.3. Checking for fragmentation

Checking the fragmentation level of BlueStore OSDs can be done either online or offline.

Prerequisites

  • A running Red Hat Ceph Storage 3.3 or higher storage cluster.
  • BlueStore OSDs.

Online BlueStore fragmentation score

  1. Inspect a running BlueStore OSD process:

    1. Simple report:

      Syntax

      ceph daemon OSD_ID bluestore allocator score block

      Example

      [root@osd ~]# ceph daemon osd.123 bluestore allocator score block

    2. A more detailed report:

      Syntax

      ceph daemon OSD_ID bluestore allocator dump block

      Example

      [root@osd ~]# ceph daemon osd.123 bluestore allocator dump block

Offline BlueStore fragmentation score

  1. Inspect a non-running BlueStore OSD process:

    1. Simple report:

      Syntax

      ceph-bluestore-tool --path PATH_TO_OSD_DATA_DIRECTORY --allocator block free-score

      Example

      [root@osd ~]# ceph-bluestore-tool --path /var/lib/ceph/osd/ceph-123 --allocator block free-score

    2. A more detailed report:

      Syntax

      ceph-bluestore-tool --path PATH_TO_OSD_DATA_DIRECTORY --allocator block free-dump

      Example

      [root@osd ~]# ceph-bluestore-tool --path /var/lib/ceph/osd/ceph-123 --allocator block free-dump

Additional Resources

9.8. How to Migrate the Object Store from FileStore to BlueStore

As a storage administrator, you can migrate from the traditional object store, FileStore, to the new object store, BlueStore.

9.8.1. Prerequisites

  • A healthy and running Red Hat Ceph Storage cluster.

9.8.2. Migrating from FileStore to BlueStore

BlueStore improves performance and robustness, compared to the traditional FileStore. A single Red Hat Ceph Storage cluster can contain a mix of both FileStore and BlueStore devices.

Converting an individual OSD cannot be done in place, or in isolation. The conversion process will rely either on the storage cluster’s normal replication and healing process or tools and strategies that copy OSD content from an old (FileStore) device to a new (BlueStore) device. There are two approach to migrate from FileStore to BlueStore.

First Approach

The first approach is to mark out each device in turn, wait for the data to replicate across the storage cluster, reprovision the OSD, and mark it back "in" again. Here are the advantages and disadvantage to this approach:

Advantages
  • Simple.
  • Can be done on a device-by-device basis.
  • No spare devices or nodes are required.
Disadvantages
  • Copying data over the network happens twice.

    Note

    One copy to some other OSD in the storage cluster, allowing you to maintain the desired number of replicas, and then another copy back to the reprovisioned BlueStore OSD.

Second Approach

The second approach is doing a whole node replacement. You need to have an empty node that has no data.

There are two ways to do this: * Starting with a new, empty node that is not part of the storage cluster. * By offloading data from an existing node in the storage cluster.

Advantages
  • Data is copied over the network only once.
  • Converts an entire node’s OSDs at once.
  • Can parallelize to converting multiple nodes at a time.
  • No spare devices are required on each node.
Disadvantages
  • A spare node is required.
  • An entire node’s worth of OSDs will be migrating data at a time. This is like likely to impact overall cluster performance.
  • All migrated data still makes one full hop over the network.

9.8.3. Migrating from FileStore to BlueStore using Ansible

Migrating from FileStore to BlueStore using Ansible will shrinks and redeploys all OSDs on the node. The Ansible playbook does a capacity check before starting the migration. The ceph-volume utility then redeploys the OSDs.

Prerequisites

  • A healthy and running Red Hat Ceph Storage 4 cluster.
  • The ansible user account for use with the Ansible application.

Procedure

  1. Log in as the ansible user on the Ansible administration node.
  2. Edit the group_vars/osd.yml file, add and set the following options:

    nb_retry_wait_osd_up: 50
    delay_wait_osd_up: 30
  3. Run the following Ansible playbook:

    Syntax

    ansible-playbook infrastructure-playbooks/filestore-to-bluestore.yml --limit OSD_NODE_TO_MIGRATE

    Example

    [ansible@admin ~]$ ansible-playbook infrastructure-playbooks/filestore-to-bluestore.yml --limit osd1

  4. Wait for the migration to complete before starting on the next OSD node in the storage cluster.

9.8.4. Migrating from FileStore to BlueStore using the mark out and replace approach

The simplest approach to migrate from FileStore to BlueStore is to mark out each device in turn, wait for the data to replicate across the storage cluster, reprovision the OSD, and mark it back "in" again.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • root access to the node.

Procedure

Replace the variable OSD_ID below with the ODS identification number.

  1. Find a FileStore OSD to replace.

    1. Get the OSD identification number:

      [root@ceph-client ~]# ceph osd tree
    2. Identify whether an OSD is using FileStore or BlueStore:

      Syntax

      ceph osd metadata OSD_ID | grep osd_objectstore

      Example

      [root@ceph-client ~]# ceph osd metadata 0 | grep osd_objectstore
          "osd_objectstore": "filestore",

    3. To view the current count of FileStore devices versus BlueStore devices:

      [root@ceph-client ~]# ceph osd count-metadata osd_objectstore
  2. Mark the FileStore OSD out:

    ceph osd out OSD_ID
  3. Wait for the data to migrate off the OSD:

    while ! ceph osd safe-to-destroy OSD_ID ; do sleep 60 ; done
  4. Stop the OSD:

    systemctl stop ceph-osd@OSD_ID
  5. Capture which device this OSD is using:

    mount | grep /var/lib/ceph/osd/ceph-OSD_ID
  6. Unmount the OSD:

    umount /var/lib/ceph/osd/ceph-OSD_ID
  7. Destroy the OSD data, using the value from step 5 as DEVICE:

    ceph-volume lvm zap DEVICE
    Important

    Be EXTREMELY CAREFUL as this will destroy the contents of the device. Be certain the data on the device is not needed, that is the storage cluster is healthy, before proceeding.``

    Note

    If the OSD is encrypted, then the unmount the osd-lockbox and remove the encryption before zapping the OSD using dmsetup remove.

    Note

    If the OSD contains logical volumes, then use the --destroy option on the ceph-volume lvm zap command.

  8. Make the storage cluster aware that the OSD has been destroyed:

    [root@ceph-client ~]# ceph osd destroy OSD_ID --yes-i-really-mean-it
  9. Reprovision the OSD as a BlueStore OSD, using DEVICE from step 5, and the same OSD_ID:

    [root@ceph-client ~]# ceph-volume lvm create --bluestore --data DEVICE --osd-id OSD_ID
  10. Repeat this procedure.

    Note

    The refilling of the new BlueStore OSD can happen concurrently with the draining of the next FileStore OSD, as long as you ensure the storage cluster is HEALTH_OK before destroying any OSDs. Failure to do so will reduce the redundancy of your data and increase the risk of, or the potentially of data loss.

9.8.5. Migrating from FileStore to BlueStore using the whole node replacement approach

Migrating from FileStore to BlueStore can be done on a node-by-node basis by transferring each stored copy of the data only once. This migration can be done with a spare node in the storage cluster, or having the sufficient free space to evacuate an entire node from the storage cluster in order to use it as a spare. Ideally, the node must have roughly the same capacity as the other nodes you will be migrating.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • root access to the node.
  • An empty node that has no data.

Procedure

  • Replace the variable NEWNODE below with the new node name.
  • Replace the variable EXISTING_NODE_TO_CONVERT below with the node name already existing in the storage cluster.
  • Replace the variable OSD_ID below with the OSD identification number.

    1. Using a new node that is not in the storage cluster. For using an existing node already in the storage cluster, skip to step 3.

      1. Add the node to the CRUSH hierarchy:

        [root@mon ~]# ceph osd crush add-bucket NEWNODE node
        Important

        Do not attach it to the root.

      2. Install the Ceph software packages:

        [root@mon ~]# yum install ceph-osd
        Note

        Copy the Ceph configuration file, by default /etc/ceph/ceph.conf, and keyrings to the new node.

    2. Skip to step 5.
    3. If you are using an existing node already in the storage cluster, use the following command:

      [root@mon ~]# ceph osd crush unlink EXISTING_NODE_TO_CONVERT default
      Note

      Where default is the immediate ancestor in the CRUSH map.

    4. Skip to step 8.
    5. Provision new BlueStore OSDs for all devices:

      [root@mon ~]# ceph-volume lvm create --bluestore --data /dev/DEVICE
    6. Verify that OSDs joined the cluster:

      [root@mon ~]# ceph osd tree

      You should see the new node name with all of the OSDs underneath the node name, but the node must not be nested underneath any other node in hierarchy.

      Example

      [root@mon ~]# ceph osd tree
      ID CLASS WEIGHT  TYPE NAME     STATUS REWEIGHT PRI-AFF
      -5             0 node newnode
      10   ssd 1.00000     osd.10        up  1.00000 1.00000
      11   ssd 1.00000     osd.11        up  1.00000 1.00000
      12   ssd 1.00000     osd.12        up  1.00000 1.00000
      -1       3.00000 root default
      -2       3.00000     node oldnode1
      0   ssd 1.00000         osd.0     up  1.00000 1.00000
      1   ssd 1.00000         osd.1     up  1.00000 1.00000
      2   ssd 1.00000         osd.2     up  1.00000 1.00000

    7. Swap the new node into the old node’s position in the cluster:

      [root@mon ~]# ceph osd crush swap-bucket NEWNODE EXISTING_NODE_TO_CONVERT

      At this point, all data on the EXISTING_NODE_TO_CONVERT will start migrating to OSDs on the NEWNODE.

      Note

      If there is a difference in the total capacity of the old and new nodes you might also see some data migrate to or from other nodes in the storage cluster, but as long as the nodes are similarly sized this will be a relatively small amount of data.

    8. Wait for data migration to complete:

      while ! ceph osd safe-to-destroy $(ceph osd ls-tree EXISTING_NODE_TO_CONVERT); do sleep 60 ; done
    9. Log into the EXISTING_NODE_TO_CONVERT, stop and unmount all old OSDs on the now-empty EXISTING_NODE_TO_CONVERT:

      [root@mon ~]# systemctl stop ceph-osd@OSD_ID
      [root@mon ~]# umount /var/lib/ceph/osd/ceph-OSD_ID
    10. Destroy and purge the old OSDs:

      for osd in ceph osd ls-tree EXISTING_NODE_TO_CONVERT; do ceph osd purge $osd --yes-i-really-mean-it ; done
    11. Wipe the old OSD devices. This requires you do identify which devices are to be wiped manually. Do the following command for each device:

      [root@mon ~]# ceph-volume lvm zap DEVICE
      Important

      Be EXTREMELY CAREFUL as this will destroy the contents of the device. Be certain the data on the device is not needed, that is the storage cluster is healthy, before proceeding.

      Note

      If the OSD is encrypted, then the unmount the osd-lockbox and remove the encryption before zapping the OSD using dmsetup remove.

      Note

      If the OSD contains logical volumes, then use the --destroy option on the ceph-volume lvm zap command.

    12. Use the now-empty old node as the new node, and repeat the process.

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