Chapter 3. Monitoring

To run the ceph utility in interactive mode, type ceph at the command line with no arguments, for example:

# ceph
ceph> health
ceph> status
ceph> quorum_status
ceph> mon_status

After you start the Ceph storage cluster, and before you start reading and/or writing data, check the storage cluster’s health first. You can check on the health of the Ceph storage cluster with the following:

# ceph health

If you specified non-default locations for the configuration or keyring, you may specify their locations:

# 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.

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

# 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:

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

# ceph df

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

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 1MB of data, the notional usage will be 1MB, but the actual usage may be 3MB or more depending on the number of replicas (e.g., size = 3, clones and snapshots.

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

# ceph status

Or:

# ceph -s

In interactive mode, type status and press Enter. :

ceph> status

Ceph will print the cluster status. 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 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

If the storage cluster has multiple monitors, which is required for high availability for production Ceph storage clusters. You should check the Ceph Monitor quorum status after you start the Ceph storage cluster before reading and/or writing data. A quorum must be present when multiple monitors are running. You should also check Ceph Monitor status periodically to ensure that they are running. If there is a problem with the Monitor, that prevents an agreement on the state of the storage cluster, the fault may prevent Ceph clients from reading and writing data.

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

In addition, using the socket is helpful when troubleshooting problems related to Monitors or OSDs. For details, see the Troubleshooting Guide for Red Hat Ceph Storage 2.

To use the socket:

ceph daemon <type>.<id> <command>

Replace:

For example, to view a Monitor status of a Monitor named mon.0:

# ceph daemon mon.0 mon_status

Alternatively, specify the daemon by using its socket file.

ceph daemon /var/run/ceph/<socket-file> <command>

For example, to view the status of an OSD named osd.2:

# ceph daemon /var/run/ceph/ceph-osd.2.asok status

To list all socket files for the Ceph processes:

$ ls /var/run/ceph

An OSD’s status is either in the cluster, in, or out of the cluster, out; and, 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, which 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.

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:

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:

# ceph osd stat

or

# 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:

# ceph osd tree

Example output:

# 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

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, for example:

# systemctl start ceph-osd@<osd_id>

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:

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.

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 (i.e., 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).

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:

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:

# 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

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:

<pool_num>.<pg_id>

Example output:

0.1f

The following subsections describe common states in greater detail.

3.2.3.1. Creating

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.

pg 1.5: up=acting: [0,1,2]
<add osd 3>
pg 1.5: up: [0,3,1] acting: [0,1,2]

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

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:

To identify stuck placement groups, execute the following:

# ceph pg dump_stuck [unclean|inactive|stale|undersized|degraded]

To store object data in the Ceph Object Store, a Ceph client must:

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

# ceph osd map <pool_name> <object_name>

This section describes what is the Red Hat Ceph Storage Dashboard and what it provides.

The Red Hat Ceph Storage Dashboard provides a monitoring dashboard for Ceph clusters to visualize the cluster state. The dashboard is accessible from a web browser and provides a number of metrics and graphs about the state of the cluster, Monitors, OSDs, Pools, or network.

The Red Hat Ceph Storage Dashboard uses the following utilities:

Main Features

The Red Hat Ceph Storage Dashboard supports the following features:

The Red Hat Ceph Storage Dashboard provides a visual dashboard to monitor various metrics in a running Ceph Storage Cluster. This section describes how to install the Red Hat Ceph Storage Dashboard.

Prerequisites

Procedure

Use the following commands on the Ansible administration node and as the root user.

This section describes how to access the Red Hat Ceph Storage Dashboard.

Prerequisites

Procedure

Additional Resources

The default user name and password for accessing the Red Hat Ceph Storage Dashboard is set to admin and admin. This section shows how to change the password after the installation.

Prerequisites

Procedure

Additional Resources

This section includes information about alerting in the Red Hat Ceph Storage Dashboard.