Configuration Guide

Red Hat Ceph Storage 4

Configuration settings for Red Hat Ceph Storage

Red Hat Ceph Storage Documentation Team

Abstract

This document provides instructions for configuring Red Hat Ceph Storage at boot time and run time. It also provides configuration reference information.

Chapter 1. The basics of Ceph configuration

As a storage administrator, you need to have a basic understanding of how to view the Ceph configuration, and how to set the Ceph configuration options for the Red Hat Ceph Storage cluster. You can view and set the Ceph configuration options at runtime.

1.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

1.2. Ceph configuration

All Red Hat Ceph Storage clusters have a configuration, which defines:

  • Cluster Identity
  • Authentication settings
  • Ceph daemons
  • Network configuration
  • Node names and addresses
  • Paths to keyrings
  • Paths to OSD log files
  • Other runtime options

A deployment tool such as Ansible will typically create an initial Ceph configuration file for you. However, you can create one yourself if you prefer to bootstrap a Red Hat Ceph Storage cluster without using a deployment tool.

1.3. The Ceph configuration file

The Ceph configuration file configures the Ceph daemons at start time, which will override their default values.

Tip

Each Ceph daemon has a series of default values, which are set by the ceph/src/common/config_opts.h file.

The location of Ceph’s default configuration file is /etc/ceph/ceph.conf. You can change that location by setting a different path by:

  • Setting the path in the $CEPH_CONF environment variable.
  • Specifying the -c command line argument, for example, -c path/ceph.conf.

Ceph configuration files use an ini style syntax. You can add comments by preceding comments with a pound sign (#) or a semi-colon (;).

Example

# <--A pound sign (#) sign precedes a comment.
# Comments always follow a semi-colon (;) or a pound (#) on each line.
# The end of the line terminates a comment.
# We recommend that you provide comments in your configuration file(s).
; A comment may be anything.

The configuration file can configure all Ceph daemons in a Ceph storage cluster or all Ceph daemons of a particular type at start time. To configure a series of daemons, the settings must be included under the processes that will receive the configuration as follows:

[global]
Description
Settings under [global] affect all daemons in a Ceph Storage Cluster.
Example
auth supported = cephx
[osd]
Description
Settings under [osd] affect all ceph-osd daemons in the Ceph storage cluster, and override the same setting in [global].
[mon]
Description
Settings under [mon] affect all ceph-mon daemons in the Ceph storage cluster, and override the same setting in [global].
Example
mon host = hostname1,hostname2,hostname3mon addr = 10.0.0.101:6789
[client]
Description
Settings under [client] affect all Ceph clients. For example, mounted Ceph block devices, Ceph object gateways, and so on.
Example
log file = /var/log/ceph/radosgw.log

Global settings affect all instances of all daemon in the Ceph storage cluster. Use the [global] heading for values that are common for all daemons in the Ceph storage cluster. You can override each [global] option by:

  • Changing the options for a particular process type:

    Example

    [osd], [mon]

OR

  • Changing the options for a particular process:

    Example

    [osd.1]

Overriding a global setting affects all child processes, except those that you specifically override in a particular daemon.

A typical global setting involves activating authentication.

Example

[global]
#Enable authentication between hosts within the cluster.
auth_cluster_required = cephx
auth_service_required = cephx
auth_client_required = cephx

You can specify settings that apply to a particular type of daemon. When you specify settings under [osd] or [mon] without specifying a particular instance, the setting will apply to all OSD or monitor daemons respectively. One example of a daemon-wide setting is the osd memory target.

Example

[osd]
osd_memory_target = 5368709120

You can specify settings for particular instances of a daemon. You may specify an instance by entering its type, delimited by a period (.) and by the instance ID. The instance ID for a Ceph OSD daemons is always numeric, but it may be alphanumeric for Ceph monitors.

Example

[osd.1]
# settings affect osd.1 only.

[mon.a]
# settings affect mon.a only.

A typical Ceph configuration file has at least the following settings:

[global]
fsid = UNIQUE_CLUSTER_ID
mon_initial_members = NODE_NAME[, NODE_NAME]
mon_host = IP_ADDRESS[, IP_ADDRESS]

#All clusters have a front-side public network.
#If you have two NICs, you can configure a back side cluster
#network for OSD object replication, heart beats, backfilling,
#recovery, and so on
public_network = PUBLIC_NET[, PUBLIC_NET]
#cluster_network = PRIVATE_NET[, PRIVATE_NET]

#Clusters require authentication by default.
auth_cluster_required = cephx
auth_service_required = cephx
auth_client_required = cephx

#Choose reasonable numbers for your number of replicas
#and placement groups.
osd_pool_default_size = NUM  # Write an object n times.
osd_pool_default_min_size = NUM # Allow writing n copy in a degraded state.
osd_pool_default_pg_num = NUM
osd_pool_default_pgp_num = NUM

#Choose a reasonable crush leaf type.
#0 for a 1-node cluster.
#1 for a multi node cluster in a single rack
#2 for a multi node, multi chassis cluster with multiple hosts in a chassis
#3 for a multi node cluster with hosts across racks, and so on
osd_crush_chooseleaf_type = NUM

1.4. Using the Ceph metavariables

Metavariables simplify Ceph storage cluster configuration dramatically. When a metavariable is set in a configuration value, Ceph expands the metavariable into a concrete value.

Metavariables are very powerful when used within the [global], [osd], [mon], or [client] sections of the Ceph configuration file. However, you can also use them with the administration socket. Ceph metavariables are similar to Bash shell expansion.

Ceph supports the following metavariables:

$cluster
Description
Expands to the Ceph storage cluster name. Useful when running multiple Ceph storage clusters on the same hardware.
Example
/etc/ceph/$cluster.keyring
Default
ceph
$type
Description
Expands to one of osd or mon, depending on the type of the instant daemon.
Example
/var/lib/ceph/$type
$id
Description
Expands to the daemon identifier. For osd.0, this would be 0.
Example
/var/lib/ceph/$type/$cluster-$id
$host
Description
Expands to the host name of the instant daemon.
$name
Description
Expands to $type.$id.
Example
/var/run/ceph/$cluster-$name.asok

1.5. Viewing the Ceph configuration at runtime

The Ceph configuration files can be viewed at boot time and run time.

Prerequisites

  • Root-level access to the Ceph node.
  • Access to admin keyring.

Procedure

  1. To view a runtime configuration, log in to a Ceph node running the daemon and execute:

    Syntax

    ceph daemon DAEMON_TYPE.ID config show

    To see the configuration for osd.0, you can log into the node containing osd.0 and execute this command:

    Example

    [root@osd ~]# ceph daemon osd.0 config show

  2. For additional options, specify a daemon and help.

    Example

    [root@osd ~]# ceph daemon osd.0 help

1.6. Viewing a specific configuration at runtime

Configuration settings for Red Hat Ceph Storage can be viewed at runtime from the Ceph Monitor node.

Prerequisites

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

Procedure

  1. Log into a Ceph node and execute:

    Syntax

    ceph daemon DAEMON_TYPE.ID config get PARAMETER

    Example

    [root@mon ~]# ceph daemon osd.0 config get public_addr

1.7. Setting a specific configuration at runtime

There are two general ways to set a runtime configuration.

  • Using the Ceph Monitor.
  • Using the Ceph administration socket.

You can set a Ceph runtime configuration option by contacting the monitor using the tell and injectargs command.

Prerequisites

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

Procedure

  1. Using the Ceph Monitor by injecting options:

    ceph tell DAEMON_TYPE.DAEMON_ID or * injectargs --NAME VALUE [--NAME VALUE]

    Replace DAEMON_TYPE with one of osd or mon.

    You can apply the runtime setting to all daemons of a particular type with *, or specify a specific DAEMON_ID, a number or name..

    For example, to change the debug logging for a ceph-osd daemon named osd.0 to 0/5, execute the following command:

    [root@osd ~]# ceph tell osd.0 injectargs '--debug-osd 0/5'
    Note

    The tell command takes multiple arguments, so each argument for tell must be within single quotes, and the configuration prepended with two dashes ('--NAME VALUE [--NAME VALUE]' ['--NAME VALUE [--NAME VALUE]']). The ceph tell command goes through the monitors.

    If you cannot bind to the monitor, you can still make the change by using the Ceph administration socket.

  2. Log into the node of the daemon whose configuration you want to change.

    1. Issue the configuration change directly to the Ceph daemon:

      [root@osd ~]# ceph osd.0 config set debug_osd 0/5
      Note

      Quotes are not necessary for the daemon command, because it only takes one argument.

1.8. OSD Memory Target

BlueStore keeps OSD heap memory usage under a designated target size with the osd_memory_target configuration option.

The option osd_memory_target sets OSD memory based upon the available RAM in the system. By default, Anisble sets the value to 4 GB. You can change the value, expressed in bytes, in the /usr/share/ceph-ansible/group_vars/all.yml file when deploying the daemon.

Example: Set the osd_memory_target to 6000000000 bytes

ceph_conf_overrides:
  osd:
    osd_memory_target=6000000000

Ceph OSD memory caching is more important when the block device is slow, for example, traditional hard drives, because the benefit of a cache hit is much higher than it would be with a solid state drive. However, this has to be weighed-in to co-locate OSDs with other services, such as in a hyper-converged infrastructure (HCI), or other applications.

Note

The value of osd_memory_target is one OSD per device for traditional hard drive device, and two OSDs per device for NVMe SSD devices. The osds_per_device is defined in group_vars/osds.yml file.

Additional Resources

1.9. MDS Memory Cache Limit

MDS servers keep their metadata in a separate storage pool, named cephfs_metadata, and are the users of Ceph OSDs. For Ceph File Systems, MDS servers have to support an entire Red Hat Ceph Storage cluster, not just a single storage device within the storage cluster, so their memory requirements can be significant, particularly if the workload consists of small-to-medium-size files, where the ratio of metadata to data is much higher.

Example: Set the mds_cache_memory_limit to 2000000000 bytes

ceph_conf_overrides:
  osd:
    mds_cache_memory_limit=2000000000
Note

For a large Red Hat Ceph Storage cluster with a metadata-intensive workload, do not put an MDS server on the same node as other memory-intensive services, doing so gives you the option to allocate more memory to MDS, for example, sizes greater than 100 GB.

Additional Resources

1.10. Additional Resources

  • See the general Ceph configuration options in Appendix A for specific option descriptions and usage.

Chapter 2. Ceph network configuration

As a storage administrator, you must understand the network environment that the Red Hat Ceph Storage cluster will operate in, and configure the Red Hat Ceph Storage accordingly. Understanding and configuring the Ceph network options will ensure optimal performance and reliability of the overall storage cluster.

2.1. Prerequisites

  • Network connectivity.
  • Installation of the Red Hat Ceph Storage software.

2.2. Network configuration for Ceph

Network configuration is critical for building a high performance Red Hat Ceph Storage cluster. The Ceph storage cluster does not perform request routing or dispatching on behalf of the Ceph client. Instead, Ceph clients make requests directly to Ceph OSD daemons. Ceph OSDs perform data replication on behalf of Ceph clients, which means replication and other factors impose additional loads on the networks of Ceph storage clusters.

All Ceph clusters must use a public network. However, unless you specify an internal cluster network, Ceph assumes a single public network. Ceph can function with a public network only, but for large storage clusters you will see significant performance improvement with a second private network for carrying only cluster-related traffic.

Important

Red Hat recommends running a Ceph storage cluster with two networks. One public network and one private network.

To support two networks, each Ceph Node will need to have more than one network interface card (NIC).

Network Architecture

There are several reasons to consider operating two separate networks:

  • Performance: Ceph OSDs handle data replication for the Ceph clients. When Ceph OSDs replicate data more than once, the network load between Ceph OSDs easily dwarfs the network load between Ceph clients and the Ceph storage cluster. This can introduce latency and create a performance problem. Recovery and rebalancing can also introduce significant latency on the public network.
  • Security: While most people are generally civil, some actors will engage in what is known as a Denial of Service (DoS) attack. When traffic between Ceph OSDs gets disrupted, peering may fail and placement groups may no longer reflect an active + clean state, which may prevent users from reading and writing data. A great way to defeat this type of attack is to maintain a completely separate cluster network that does not connect directly to the internet.

Network configuration settings are not required. Ceph can function with a public network only, assuming a public network is configured on all hosts running a Ceph daemon. However, Ceph allows you to establish much more specific criteria, including multiple IP networks and subnet masks for your public network. You can also establish a separate cluster network to handle OSD heartbeat, object replication, and recovery traffic.

Do not confuse the IP addresses you set in the configuration with the public-facing IP addresses network clients might use to access your service. Typical internal IP networks are often 192.168.0.0 or 10.0.0.0.

Note

Ceph uses CIDR notation for subnets, for example, 10.0.0.0/24.

Important

If you specify more than one IP address and subnet mask for either the public or the private network, the subnets within the network must be capable of routing to each other. Additionally, make sure you include each IP address and subnet in your IP tables and open ports for them as necessary.

When you configured the networks, you can restart the cluster or restart each daemon. Ceph daemons bind dynamically, so you do not have to restart the entire cluster at once if you change the network configuration.

2.3. Configuration requirements for Ceph daemons

Ceph has one network configuration requirement that applies to all daemons. The Ceph configuration file must specify the host for each daemon.

Important

Some deployment utilities might create a configuration file for you. Do not set these values if the deployment utility does it for you.

Important

The host option is the short name of the node, not its FQDN. It is not an IP address.

You can set the host names and the IP addresses for where the daemon resides by specifying the host name.

Example

[mon.a]
    host = HOSTNAME
    mon_addr = IP_ADDRESS:6789

[osd.0]
    host = HOSTNAME

You do not have to set the node IP address for a daemon, it is optional. If you have a static IP configuration and both public and private networks running, the Ceph configuration file might specify the IP address of the node for each daemon. Setting a static IP address for a daemon must appear in the daemon instance sections of the Ceph configuration file.

[osd.0]
    public_addr = NODE_PUBLIC_IP_ADDRESS
    cluster_addr = NODE_PRIVATE_IP_ADDRESS

You can deploy an OSD host with a single NIC in a cluster with two networks by forcing the OSD host. You can force the OSD host to operate on the public network by adding a public addr entry to the [osd.n] section of the Ceph configuration file, where n refers to the number of the OSD with one NIC. Additionally, the public network and cluster network must be able to route traffic to each other, which Red Hat does not recommend for security reasons.

Important

Red Hat does not recommend deploying an OSD node with a single NIC with two networks for security reasons.

Additional Resources

  • See the host options in Red Hat Ceph Storage Configuration Guide, Appendix B for specific option descriptions and usage.
  • See the common options in Red Hat Ceph Storage Configuration Guide, Appendix B for specific option descriptions and usage.

2.4. Ceph network messenger

Messenger is the Ceph network layer implementation. Red Hat supports two messenger types:

  • simple
  • async

In Red Hat Ceph Storage 3 and higher, async is the default messenger type. To change the messenger type, specify the ms_type configuration setting in the [global] section of the Ceph configuration file.

Note

For the async messenger, Red Hat supports the posix transport type, but does not currently support rdma or dpdk. By default, the ms_type setting in Red Hat Ceph Storage 3 or higher reflects async+posix, where async is the messenger type and posix is the transport type.

SimpleMessenger

The SimpleMessenger implementation uses TCP sockets with two threads per socket. Ceph associates each logical session with a connection. A pipe handles the connection, including the input and output of each message. While SimpleMessenger is effective for the posix transport type, it is not effective for other transport types such as rdma or dpdk.

AsyncMessenger

Consequently, AsyncMessenger is the default messenger type for Red Hat Ceph Storage 3 or higher. For Red Hat Ceph Storage 3 or higher, the AsyncMessenger implementation uses TCP sockets with a fixed-size thread pool for connections, which should be equal to the highest number of replicas or erasure-code chunks. The thread count can be set to a lower value if performance degrades due to a low CPU count or a high number of OSDs per server.

Note

Red Hat does not support other transport types such as rdma or dpdk at this time.

Additional Resources

  • See the AsyncMessenger options in Red Hat Ceph Storage Configuration Guide, Appendix B for specific option descriptions and usage.
  • See the Red Hat Ceph Storage Architecture Guide for details about using on-wire encryption with the Ceph messenger version 2 protocol.

2.5. Configuring a public network

The public network configuration allows you specifically define IP addresses and subnets for the public network. You may specifically assign static IP addresses or override public network settings using the public addr setting for a specific daemon.

Prerequisites

  • Installation of the Red Hat Ceph Storage software.

Procedure

  1. Add the following option to the [global] section of the Ceph configuration file:
[global]
    ...
    public_network = PUBLIC-NET/NETMASK

Additional Resources

  • See the common options in Red Hat Ceph Storage Configuration Guide, Appendix B for specific option descriptions and usage.

2.6. Configuring a private network

If you declare a cluster network, OSDs will route heartbeat, object replication, and recovery traffic over the cluster network. This can improve performance compared to using a single network.

Important

It is preferable, that the cluster network is not reachable from the public network or the Internet for added security.

The cluster network configuration allows you to declare a cluster network, and specifically define IP addresses and subnets for the cluster network. You can specifically assign static IP addresses or override cluster network settings using the cluster addr setting for specific OSD daemons.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Access to the Ceph software repository.

Procedure

  1. Add the following option to the [global] section of the Ceph configuration file:
[global]
    ...
    cluster_network = CLUSTER-NET/NETMASK

2.7. Verify the firewall settings

By default, daemons bind to ports within the 6800:7100 range. You can configure this range at your discretion. Before configuring the firewall, check the default firewall configuration.

Prerequisites

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

Procedure

  1. You can configure this range at your discretion:

    [root@mon ~]# sudo iptables -L
  2. For the firewalld daemon, execute the following command:

    [root@mon ~]# firewall-cmd --list-all-zones

    Some Linux distributions include rules that reject all inbound requests except SSH from all network interfaces.

    Example

    REJECT all -- anywhere anywhere reject-with icmp-host-prohibited

2.8. Firewall settings for Ceph Monitor node

Ceph monitors listen on port 6789 by default. Additionally, Ceph monitors always operate on the public network.

Prerequisites

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

Procedure

  1. Add rules using the following example:

    [root@mon ~]# sudo iptables -A INPUT -i IFACE -p tcp -s IP-ADDRESS/NETMASK --dport 6789 -j ACCEPT
    1. Replace IFACE with the public network interface (for example, eth0, eth1, and so on).
    2. Replace IP-ADDRESS with the IP address of the public network and NETMASK with the netmask for the public network.
  2. For the firewalld daemon, execute the following commands:

    [root@mon ~]# firewall-cmd --zone=public --add-port=6789/tcp
    [root@mon ~]# firewall-cmd --zone=public --add-port=6789/tcp --permanent

2.9. Firewall settings for Ceph OSDs

By default, Ceph OSDs bind to the first available ports on a Ceph node beginning at port 6800. Ensure to open at least four ports beginning at port 6800 for each OSD that runs on the node:

  • One for talking to clients and monitors on the public network.
  • One for sending data to other OSDs on the cluster network.
  • Two for sending heartbeat packets on the cluster network.
OSD Firewall

Ports are node-specific. However, you might need to open more ports than the number of ports needed by Ceph daemons running on that Ceph node in the event that processes get restarted and the bound ports do not get released. Consider to open a few additional ports in case a daemon fails and restarts without releasing the port such that the restarted daemon binds to a new port. Also, consider opening the port range of 6800:7300 on each OSD node.

If you set separate public and cluster networks, you must add rules for both the public network and the cluster network, because clients will connect using the public network and other Ceph OSD Daemons will connect using the cluster network.

Prerequisites

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

Procedure

  1. Add rules using the following example:

    [root@mon ~]# sudo iptables -A INPUT -i IFACE  -m multiport -p tcp -s IP-ADDRESS/NETMASK --dports 6800:6810 -j ACCEPT
    1. Replace IFACE with the public network interface (for example, eth0, eth1, and so on).
    2. Replace IP-ADDRESS with the IP address of the public network and NETMASK with the netmask for the public network.
  2. For the firewalld daemon, execute the following:

    [root@mon ~] # firewall-cmd --zone=public --add-port=6800-6810/tcp
    [root@mon ~] # firewall-cmd --zone=public --add-port=6800-6810/tcp --permanent

If you put the cluster network into another zone, open the ports within that zone as appropriate.

2.10. Additional Resources

  • See the Red Hat Ceph Storage network configuration options in Appendix B for specific option descriptions and usage.
  • See the Red Hat Ceph Storage Architecture Guide for details about using on-wire encryption with the Ceph messenger version 2 protocol.

Chapter 3. Ceph Monitor configuration

As a storage administrator, you can use the default configuration values for the Ceph Monitor or customize them according to the intended workload.

3.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

3.2. Ceph Monitor configuration

Understanding how to configure a Ceph Monitor is an important part of building a reliable Red Hat Ceph Storage cluster. All clusters have at least one monitor. A monitor configuration usually remains fairly consistent, but you can add, remove or replace a monitor in a cluster.

Ceph monitors maintain a "master copy" of the cluster map. That means a Ceph client can determine the location of all Ceph monitors and Ceph OSDs just by connecting to one Ceph monitor and retrieving a current cluster map.

Before Ceph clients can read from or write to Ceph OSDs, they must connect to a Ceph monitor first. With a current copy of the cluster map and the CRUSH algorithm, a Ceph client can compute the location for any object. The ability to compute object locations allows a Ceph client to talk directly to Ceph OSDs, which is a very important aspect of Ceph high scalability and performance.

The primary role of the Ceph monitor is to maintain a master copy of the cluster map. Ceph monitors also provide authentication and logging services. Ceph monitors write all changes in the monitor services to a single Paxos instance, and Paxos writes the changes to a key-value store for strong consistency. Ceph monitors can query the most recent version of the cluster map during synchronization operations. Ceph monitors leverage the key-value store’s snapshots and iterators (using the leveldb database) to perform store-wide synchronization.

Paxos

3.3. Ceph cluster maps

The cluster map is a composite of maps, including the monitor map, the OSD map, and the placement group map. The cluster map tracks a number of important events:

  • Which processes are in the Red Hat Ceph Storage cluster.
  • Which processes that are in the Red Hat Ceph Storage cluster are up and running or down.
  • Whether, the placement groups are active or inactive, and clean or in some other state.
  • other details that reflect the current state of the cluster such as:

    • the total amount of storage space or
    • the amount of storage used.

When there is a significant change in the state of the cluster for example, a Ceph OSD goes down, a placement group falls into a degraded state, and so on. The cluster map gets updated to reflect the current state of the cluster. Additionally, the Ceph monitor also maintains a history of the prior states of the cluster. The monitor map, OSD map, and placement group map each maintain a history of their map versions. Each version is called an epoch.

When operating the Red Hat Ceph Storage cluster, keeping track of these states is an important part of the cluster administration.

3.4. Ceph Monitor quorum

A cluster will run sufficiently with a single monitor. However, a single monitor is a single-point-of-failure. To ensure high availability in a production Ceph storage cluster, run Ceph with multiple monitors so that the failure of a single monitor will not cause a failure of the entire storage cluster.

When a Ceph storage cluster runs multiple Ceph Monitors for high availability, Ceph Monitors use the Paxos algorithm to establish consensus about the master cluster map. A consensus requires a majority of monitors running to establish a quorum for consensus about the cluster map. For example, 1; 2 out of 3; 3 out of 5; 4 out of 6; and so on.

Red Hat recommends running a production Red Hat Ceph Storage cluster with at least three Ceph Monitors to ensure high availability. When you run multiple monitors, you can specify the initial monitors that must be members of the storage cluster in order to establish a quorum. This may reduce the time it takes for the storage cluster to come online.

[mon]
mon_initial_members = a,b,c
Note

A majority of the monitors in the storage cluster must be able to reach each other in order to establish a quorum. You can decrease the initial number of monitors to establish a quorum with the mon_initial_members option.

3.5. Ceph Monitor consistency

When you add monitor settings to the Ceph configuration file, you need to be aware of some of the architectural aspects of Ceph Monitors. Ceph imposes strict consistency requirements for a Ceph Monitor when discovering another Ceph Monitor within the cluster. Whereas, Ceph clients and other Ceph daemons use the Ceph configuration file to discover monitors, monitors discover each other using the monitor map (monmap), not the Ceph configuration file.

A Ceph Monitor always refers to the local copy of the monitor map when discovering other Ceph Monitors in the Red Hat Ceph Storage cluster. Using the monitor map instead of the Ceph configuration file avoids errors that could break the cluster. For example, typos in the Ceph configuration file when specifying a monitor address or port. Since monitors use monitor maps for discovery and they share monitor maps with clients and other Ceph daemons, the monitor map provides monitors with a strict guarantee that their consensus is valid.

Strict consistency when applying updates to the monitor maps

As with any other updates on the Ceph Monitor, changes to the monitor map always run through a distributed consensus algorithm called Paxos. The Ceph Monitors must agree on each update to the monitor map, such as adding or removing a Ceph Monitor, to ensure that each monitor in the quorum has the same version of the monitor map. Updates to the monitor map are incremental so that Ceph Monitors have the latest agreed upon version, and a set of previous versions.

Maintaining history

Maintaining a history enables a Ceph Monitor that has an older version of the monitor map to catch up with the current state of the Red Hat Ceph Storage cluster.

If Ceph Monitors discovered each other through the Ceph configuration file instead of through the monitor map, it would introduce additional risks because the Ceph configuration files are not updated and distributed automatically. Ceph Monitors might inadvertently use an older Ceph configuration file, fail to recognize a Ceph Monitor, fall out of a quorum, or develop a situation where Paxos is not able to determine the current state of the system accurately.

3.6. Bootstrap the Ceph Monitor

In most configuration and deployment cases, tools that deploy Ceph such as Ansible might help bootstrap the Ceph monitors by generating a monitor map for you.

A Ceph monitor requires a few explicit settings:

  • File System ID: The fsid is the unique identifier for your object store. Since you can run multiple storage clusters on the same hardware, you must specify the unique ID of the object store when bootstrapping a monitor. Using deployment tools, such as Ansible will generate a file system identifier, but you can specify the fsid manually too.
  • Monitor ID: A monitor ID is a unique ID assigned to each monitor within the cluster. It is an alphanumeric value, and by convention the identifier usually follows an alphabetical increment. For example, a, b, and so on. This can be set in the Ceph configuration file. For example, [mon.a], [mon.b], and so on, by a deployment tool, or using the ceph command.
  • Keys: The monitor must have secret keys.

3.7. Ceph Monitor section in the configuration file

To apply configuration settings to the entire cluster, enter the configuration settings under the [global] section. To apply configuration settings to all monitors in the cluster, enter the configuration settings under the [mon] section. To apply configuration settings to specific monitors, specify the monitor instance.

Example

[mon.a]

By convention, monitor instance names use alpha notation.

[global]

[mon]

[mon.a]

[mon.b]

[mon.c]

3.8. Minimum configuration for a Ceph Monitor

The bare minimum monitor settings for a Ceph monitor in the Ceph configuration file includes a host name for each monitor if it is not configured for DNS and the monitor address. You can configure these under [mon] or under the entry for a specific monitor.

[mon]
mon_host = hostname1,hostname2,hostname3
mon_addr = 10.0.0.10:6789,10.0.0.11:6789,10.0.0.12:6789

Or

[mon.a]
host = hostname1
mon_addr = 10.0.0.10:6789
Note

This minimum configuration for monitors assumes that a deployment tool generates the fsid and the mon. key for you.

Important

Once you deploy a Ceph cluster, do not change the IP address of the monitors.

As of RHCS 2.4, Ceph does not require the mon_host when the cluster is configured to look up a monitor via the DNS server. To configure the Ceph cluster for DNS lookup, set the mon_dns_srv_name setting in the Ceph configuration file.

Once set, configure the DNS. Create records either IPv4 (A) or IPv6 (AAAA) for the monitors in the DNS zone.

Example

#IPv4
mon1.example.com. A 192.168.0.1
mon2.example.com. A 192.168.0.2
mon3.example.com. A 192.168.0.3

#IPv6
mon1.example.com. AAAA 2001:db8::100
mon2.example.com. AAAA 2001:db8::200
mon3.example.com. AAAA 2001:db8::300

Where: example.com is the DNS search domain.

Then, create the SRV TCP records with the name mon_dns_srv_name configuration setting pointing to the three Monitors. The following example uses the default ceph-mon value.

Example

_ceph-mon._tcp.example.com. 60 IN SRV 10 60 6789 mon1.example.com.
_ceph-mon._tcp.example.com. 60 IN SRV 10 60 6789 mon2.example.com.
_ceph-mon._tcp.example.com. 60 IN SRV 10 60 6789 mon3.example.com.

Monitors run on port 6789 by default, and their priority and weight are all set to 10 and 60 respectively in the foregoing example.

3.9. Unique identifier for Ceph

Each Red Hat Ceph Storage cluster has a unique identifier (fsid). If specified, it usually appears under the [global] section of the configuration file. Deployment tools usually generate the fsid and store it in the monitor map, so the value may not appear in a configuration file. The fsid makes it possible to run daemons for multiple clusters on the same hardware.

Note

Do not set this value if you use a deployment tool that does it for you.

3.10. Ceph Monitor data store

Ceph provides a default path where Ceph monitors store data.

Important

Red Hat recommends running Ceph monitors on separate hosts and drives from Ceph OSDs for optimal performance in a production Red Hat Ceph Storage cluster.

Ceph monitors call the fsync() function often, which can interfere with Ceph OSD workloads.

Ceph monitors store their data as key-value pairs. Using a data store prevents recovering Ceph monitors from running corrupted versions through Paxos, and it enables multiple modification operations in one single atomic batch, among other advantages.

Important

Red Hat does not recommend changing the default data location. If you modify the default location, make it uniform across Ceph monitors by setting it in the [mon] section of the configuration file.

3.11. Ceph storage capacity

When a Red Hat Ceph Storage cluster gets close to its maximum capacity (specifies by the mon_osd_full_ratio parameter), Ceph prevents you from writing to or reading from Ceph OSDs as a safety measure to prevent data loss. Therefore, letting a production Red Hat Ceph Storage cluster approach its full ratio is not a good practice, because it sacrifices high availability. The default full ratio is .95, or 95% of capacity. This a very aggressive setting for a test cluster with a small number of OSDs.

Tip

When monitoring a cluster, be alert to warnings related to the nearfull ratio. This means that a failure of some OSDs could result in a temporary service disruption if one or more OSDs fails. Consider adding more OSDs to increase storage capacity.

A common scenario for test clusters involves a system administrator removing a Ceph OSD from the Red Hat Ceph Storage cluster to watch the cluster re-balance. Then, removing another Ceph OSD, and so on until the Red Hat Ceph Storage cluster eventually reaches the full ratio and locks up.

Important

Red Hat recommends a bit of capacity planning even with a test cluster. Planning enables you to gauge how much spare capacity you will need in order to maintain high availability.

Ideally, you want to plan for a series of Ceph OSD failures where the cluster can recover to an active + clean state without replacing those Ceph OSDs immediately. You can run a cluster in an active + degraded state, but this is not ideal for normal operating conditions.

The following diagram depicts a simplistic Red Hat Ceph Storage cluster containing 33 Ceph Nodes with one Ceph OSD per host, each Ceph OSD Daemon reading from and writing to a 3TB drive. So this exemplary Red Hat Ceph Storage cluster has a maximum actual capacity of 99TB. With a mon osd full ratio of 0.95, if the Red Hat Ceph Storage cluster falls to 5 TB of remaining capacity, the cluster will not allow Ceph clients to read and write data. So the Red Hat Ceph Storage cluster’s operating capacity is 95 TB, not 99 TB.

Storage Capacity

It is normal in such a cluster for one or two OSDs to fail. A less frequent but reasonable scenario involves a rack’s router or power supply failing, which brings down multiple OSDs simultaneously for example, OSDs 7-12. In such a scenario, you should still strive for a cluster that can remain operational and achieve an active + clean state, even if that means adding a few hosts with additional OSDs in short order. If your capacity utilization is too high, you might not lose data, but you could still sacrifice data availability while resolving an outage within a failure domain if capacity utilization of the cluster exceeds the full ratio. For this reason, Red Hat recommends at least some rough capacity planning.

Identify two numbers for your cluster:

  • the number of OSDs
  • the total capacity of the cluster

To determine the mean average capacity of an OSD within a cluster, divide the total capacity of the cluster by the number of OSDs in the cluster. Consider multiplying that number by the number of OSDs you expect to fail simultaneously during normal operations (a relatively small number). Finally, multiply the capacity of the cluster by the full ratio to arrive at a maximum operating capacity. Then, subtract the number of amount of data from the OSDs you expect to fail to arrive at a reasonable full ratio. Repeat the foregoing process with a higher number of OSD failures (for example, a rack of OSDs) to arrive at a reasonable number for a near full ratio.

3.12. Ceph heartbeat

Ceph monitors know about the cluster by requiring reports from each OSD, and by receiving reports from OSDs about the status of their neighboring OSDs. Ceph provides reasonable default settings for interaction between monitor and OSD, however, you can modify them as needed.

3.13. Ceph Monitor synchronization role

When you run a production cluster with multiple monitors which is recommended, each monitor checks to see if a neighboring monitor has a more recent version of the cluster map. For example, a map in a neighboring monitor with one or more epoch numbers higher than the most current epoch in the map of the instant monitor. Periodically, one monitor in the cluster might fall behind the other monitors to the point where it must leave the quorum, synchronize to retrieve the most current information about the cluster, and then rejoin the quorum.

Synchronization roles

For the purposes of synchronization, monitors can assume one of three roles:

  • Leader: The Leader is the first monitor to achieve the most recent Paxos version of the cluster map.
  • Provider: The Provider is a monitor that has the most recent version of the cluster map, but was not the first to achieve the most recent version.
  • Requester: The Requester is a monitor that has fallen behind the leader and must synchronize in order to retrieve the most recent information about the cluster before it can rejoin the quorum.

These roles enable a leader to delegate synchronization duties to a provider, which prevents synchronization requests from overloading the leader and improving performance. In the following diagram, the requester has learned that it has fallen behind the other monitors. The requester asks the leader to synchronize, and the leader tells the requester to synchronize with a provider.

Monitor Synchronization

Monitor synchronization

Synchronization always occurs when a new monitor joins the cluster. During runtime operations, monitors can receive updates to the cluster map at different times. This means the leader and provider roles may migrate from one monitor to another. If this happens while synchronizing for example, a provider falls behind the leader, the provider can terminate synchronization with a requester.

Once synchronization is complete, Ceph requires trimming across the cluster. Trimming requires that the placement groups are active + clean.

3.14. Ceph time synchronization

Ceph daemons pass critical messages to each other, which must be processed before daemons reach a timeout threshold. If the clocks in Ceph monitors are not synchronized, it can lead to a number of anomalies.

For example:

  • Daemons ignoring received messages such as outdated timestamps.
  • Timeouts triggered too soon or late when a message was not received in time.
Tip

Install NTP on the Ceph monitor hosts to ensure that the monitor cluster operates with synchronized clocks.

Clock drift may still be noticeable with NTP even though the discrepancy is not yet harmful. Ceph clock drift and clock skew warnings can get triggered even though NTP maintains a reasonable level of synchronization. Increasing your clock drift may be tolerable under such circumstances. However, a number of factors such as workload, network latency, configuring overrides to default timeouts and other synchronization options that can influence the level of acceptable clock drift without compromising Paxos guarantees.

Additional Resources

3.15. Additional Resources

  • See all the Red Hat Ceph Storage Monitor configuration options in Appendix C for specific option descriptions and usage.

Chapter 4. Ceph authentication configuration

As a storage administrator, authenticating users and services is important to the security of the Red Hat Ceph Storage cluster. Red Hat Ceph Storage includes the Cephx protocol, as the default, for cryptographic authentication, and the tools to manage authentication in the storage cluster.

4.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

4.2. Cephx authentication

The cephx protocol is enabled by default. Cryptographic authentication has some computational costs, though they are generally quite low. If the network environment connecting clients and hosts is considered safe and you cannot afford authentication computational costs, you can disable it. When deploying a Ceph storage cluster, the deployment tool will create the client.admin user and keyring.

Important

Red Hat recommends using authentication.

Note

If you disable authentication, you are at risk of a man-in-the-middle attack altering client and server messages, which could lead to significant security issues.

Enabling and disabling Cephx

Enabling Cephx requires that you have deployed keys for the Ceph Monitors and OSDs. When toggling Cephx authentication on or off, you do not have to repeat the deployment procedures.

4.3. Enabling Cephx

When cephx is enabled, Ceph will look for the keyring in the default search path, which includes /etc/ceph/$cluster.$name.keyring. You can override this location by adding a keyring option in the [global] section of the Ceph configuration file, but this is not recommended.

Execute the following procedures to enable cephx on a cluster with authentication disabled. If you or your deployment utility have already generated the keys, you may skip the steps related to generating keys.

Prerequisites

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

Procedure

  1. Create a client.admin key, and save a copy of the key for your client host:

    [root@mon ~]# ceph auth get-or-create client.admin mon 'allow *' osd 'allow *' -o /etc/ceph/ceph.client.admin.keyring
    Warning

    This will erase the contents of any existing /etc/ceph/client.admin.keyring file. Do not perform this step if a deployment tool has already done it for you.

  2. Create a keyring for the monitor cluster and generate a monitor secret key:

    [root@mon ~]# ceph-authtool --create-keyring /tmp/ceph.mon.keyring --gen-key -n mon. --cap mon 'allow *'
  3. Copy the monitor keyring into a ceph.mon.keyring file in every monitor mon data directory. For example, to copy it to mon.a in cluster ceph, use the following:

    [root@mon ~]# cp /tmp/ceph.mon.keyring /var/lib/ceph/mon/ceph-a/keyring
  4. Generate a secret key for every OSD, where ID is the OSD number:

    ceph auth get-or-create osd.ID mon 'allow rwx' osd 'allow *' -o /var/lib/ceph/osd/ceph-ID/keyring
  5. By default the cephx authentication protocol is enabled.

    Note

    If the cephx authentication protocol was disabled previously by setting the authentication options to none, then by removing the following lines under the [global] section in the Ceph configuration file (/etc/ceph/ceph.conf) will reenable the cephx authentication protocol:

    auth_cluster_required = none
    auth_service_required = none
    auth_client_required = none
  6. Start or restart the Ceph storage cluster.

    Important

    Enabling cephx requires downtime because the cluster needs to be completely restarted, or it needs to be shut down and then started while client I/O is disabled.

    These flags need to be set before restarting or shutting down the storage cluster:

    [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

    Once cephx is enabled and all PGs are active and clean, unset the flags:

    [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

4.4. Disabling Cephx

The following procedure describes how to disable Cephx. If your cluster environment is relatively safe, you can offset the computation expense of running authentication.

Important

Red Hat recommends enabling authentication.

However, it may be easier during setup or troubleshooting to temporarily disable authentication.

Prerequisites

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

Procedure

  1. Disable cephx authentication by setting the following options in the [global] section of the Ceph configuration file:

    auth_cluster_required = none
    auth_service_required = none
    auth_client_required = none
  2. Start or restart the Ceph storage cluster.

4.5. Cephx user keyrings

When you run Ceph with authentication enabled, the ceph administrative commands and Ceph clients require authentication keys to access the Ceph storage cluster.

The most common way to provide these keys to the ceph administrative commands and clients is to include a Ceph keyring under the /etc/ceph/ directory. The file name is usually ceph.client.admin.keyring or $cluster.client.admin.keyring. If you include the keyring under the /etc/ceph/ directory, you do not need to specify a keyring entry in the Ceph configuration file.

Important

Red Hat recommends copying the Red Hat Ceph Storage cluster keyring file to nodes where you will run administrative commands, because it contains the client.admin key.

To do so, execute the following command:

# scp USER@HOSTNAME:/etc/ceph/ceph.client.admin.keyring /etc/ceph/ceph.client.admin.keyring

Replace USER with the user name used on the host with the client.admin key and HOSTNAME with the host name of that host.

Note

Ensure the ceph.keyring file has appropriate permissions set on the client machine.

You can specify the key itself in the Ceph configuration file using the key setting, which is not recommended, or a path to a key file using the keyfile setting.

4.6. Cephx daemon keyrings

Administrative users or deployment tools might generate daemon keyrings in the same way as generating user keyrings. By default, Ceph stores daemons keyrings inside their data directory. The default keyring locations, and the capabilities necessary for the daemon to function.

Note

The monitor keyring contains a key but no capabilities, and is not part of the Ceph storage cluster auth database.

The daemon data directory locations default to directories of the form:

/var/lib/ceph/$type/CLUSTER-ID

Example

/var/lib/ceph/osd/ceph-12

You can override these locations, but it is not recommended.

4.7. Cephx message signatures

Ceph provides fine-grained control so you can enable or disable signatures for service messages between the client and Ceph. You can enable or disable signatures for messages between Ceph daemons.

Important

Red Hat recommends that Ceph authenticate all ongoing messages between the entities using the session key set up for that initial authentication.

Note

Ceph kernel modules do not support signatures yet.

4.8. Additional Resources

  • See all the Red Hat Ceph Storage Cephx configuration options in Appendix D for specific option descriptions and usage.

Chapter 5. Pools, placement groups, and CRUSH configuration

As a storage administrator, you can choose to use the Red Hat Ceph Storage default options for pools, placement groups, and the CRUSH algorithm or customize them for the intended workload.

5.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

5.2. Pools placement groups and CRUSH

When you create pools and set the number of placement groups for the pool, Ceph uses default values when you do not specifically override the defaults.

Important

Red Hat recommends overriding some of the defaults. Specifically, set a pool’s replica size and override the default number of placement groups.

You can set these values when running pool commands. You can also override the defaults by adding new ones in the [global] section of the Ceph configuration file.

Example

[global]

# By default, Ceph makes 3 replicas of objects. If you want to set 4
# copies of an object as the default value--a primary copy and three replica
# copies--reset the default values as shown in 'osd pool default size'.
# If you want to allow Ceph to write a lesser number of copies in a degraded
# state, set 'osd pool default min size' to a number less than the
# 'osd pool default size' value.

osd_pool_default_size = 4  # Write an object 4 times.
osd_pool_default_min_size = 1 # Allow writing one copy in a degraded state.

# Ensure you have a realistic number of placement groups. We recommend
# approximately 100 per OSD. E.g., total number of OSDs multiplied by 100
# divided by the number of replicas (i.e., osd pool default size). So for
# 10 OSDs and osd pool default size = 4, we'd recommend approximately
# (100 * 10) / 4 = 250.

osd_pool_default_pg_num = 250
osd_pool_default_pgp_num = 250

5.3. Additional Resources

  • See all the Red Hat Ceph Storage pool, placement group, and CRUSH configuration options in Appendix E for specific option descriptions and usage.

Chapter 6. Ceph Object Storage Daemon (OSD) configuration

As a storage administrator, you can configure the Ceph Object Storage Daemon (OSD) to be redundant and optimized based on the intended workload.

6.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

6.2. Ceph OSD configuration

All Ceph clusters have a configuration, which defines:

  • Cluster identity
  • Authentication settings
  • Ceph daemon membership in the cluster
  • Network configuration
  • Host names and addresses
  • Paths to keyrings
  • Paths to OSD log files
  • Other runtime options

A deployment tool such as Red Hat Ceph Storage Console or Ansible will typically create an initial Ceph configuration file for you. However, you can create one yourself if you prefer to bootstrap a cluster without using a deployment tool.

For your convenience, each daemon has a series of default values, that is, many are set by the ceph/src/common/config_opts.h script. You can override these settings with a Ceph configuration file or at runtime by using the monitor tell command or connecting directly to a daemon socket on a Ceph node.

Important

Red Hat does not recommend changing the default paths, as it makes it more problematic to troubleshoot Ceph later.

6.3. Scrubbing the OSD

In addition to making multiple copies of objects, Ceph insures data integrity by scrubbing placement groups. Ceph scrubbing is analogous to the fsck command on the object storage layer.

For each placement group, Ceph generates a catalog of all objects and compares each primary object and its replicas to ensure that no objects are missing or mismatched.

Light scrubbing (daily) checks the object size and attributes. Deep scrubbing (weekly) reads the data and uses checksums to ensure data integrity.

Scrubbing is important for maintaining data integrity, but it can reduce performance. Adjust the following settings to increase or decrease scrubbing operations.

6.4. Backfilling an OSD

When you add Ceph OSDs to a cluster or remove them from the cluster, the CRUSH algorithm rebalances the cluster by moving placement groups to or from Ceph OSDs to restore the balance. The process of migrating placement groups and the objects they contain can reduce the cluster operational performance considerably. To maintain operational performance, Ceph performs this migration with the 'backfill' process, which allows Ceph to set backfill operations to a lower priority than requests to read or write data.

6.5. OSD recovery

When the cluster starts or when a Ceph OSD terminates unexpectedly and restarts, the OSD begins peering with other Ceph OSDs before write operation can occur.

If a Ceph OSD crashes and comes back online, usually it will be out of sync with other Ceph OSDs containing more recent versions of objects in the placement groups. When this happens, the Ceph OSD goes into recovery mode and seeks to get the latest copy of the data and bring its map back up to date. Depending upon how long the Ceph OSD was down, the OSD’s objects and placement groups may be significantly out of date. Also, if a failure domain went down for example, a rack, more than one Ceph OSD may come back online at the same time. This can make the recovery process time consuming and resource intensive.

To maintain operational performance, Ceph performs recovery with limitations on the number recovery requests, threads and object chunk sizes which allows Ceph perform well in a degraded state.

6.6. Additional Resources

  • See all the Red Hat Ceph Storage Ceph OSD configuration options in Appendix F for specific option descriptions and usage.

Chapter 7. Ceph Monitor and OSD interaction configuration

As a storage administrator, you must properly configure the interactions between the Ceph Monitors and OSDs to ensure a stable working environment.

7.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

7.2. Ceph Monitor and OSD interaction

After you have completed your initial Ceph configuration, you can deploy and run Ceph. When you execute a command such as ceph health or ceph -s, the Ceph Monitor reports on the current state of the Ceph storage cluster. The Ceph Monitor knows about the Ceph storage cluster by requiring reports from each Ceph OSD daemon, and by receiving reports from Ceph OSD daemons about the status of their neighboring Ceph OSD daemons. If the Ceph Monitor does not receive reports, or if it receives reports of changes in the Ceph storage cluster, the Ceph Monitor updates the status of the Ceph cluster map.

Ceph provides reasonable default settings for Ceph Monitor and OSD interaction. However, you can override the defaults. The following sections describe how Ceph Monitors and Ceph OSD daemons interact for the purposes of monitoring the Ceph storage cluster.

7.3. OSD heartbeat

Each Ceph OSD daemon checks the heartbeat of other Ceph OSD daemons every 6 seconds. To change the heartbeat interval, add the osd heartbeat interval setting under the [osd] section of the Ceph configuration file, or change its value at runtime.

If a neighboring Ceph OSD daemon does not send heartbeat packets within a 20 second grace period, the Ceph OSD daemon might consider the neighboring Ceph OSD daemon down. It can report it back to a Ceph Monitor, which will update the Ceph cluster map. To change this grace period, add the osd heartbeat grace setting under the [osd] section of the Ceph configuration file, or set its value at runtime.

Check Heartbeats

7.4. Reporting an OSD as down

By default, two Ceph OSD Daemons from different hosts must report to the Ceph Monitors that another Ceph OSD Daemon is down before the Ceph Monitors acknowledge that the reported Ceph OSD Daemon is down.

However, there is chance that all the OSDs reporting the failure are in different hosts in a rack with a bad switch that causes connection problems between OSDs.

To avoid a "false alarm," Ceph considers the peers reporting the failure as a proxy for a "subcluster" that is similarly laggy. While this is not always the case, it may help administrators localize the grace correction to a subset of the system that is performing poorly.

Ceph uses the mon_osd_reporter_subtree_level setting to group the peers into the "subcluster" by their common ancestor type in the CRUSH map.

By default, only two reports from a different subtree are required to report another Ceph OSD Daemon down. Administrators can change the number of reporters from unique subtrees and the common ancestor type required to report a Ceph OSD Daemon down to a Ceph Monitor by adding the mon_osd_min_down_reporters and mon_osd_reporter_subtree_level settings under the [mon] section of the Ceph configuration file, or by setting the value at runtime.

Report Down OSDs

7.5. Reporting a peering failure

If a Ceph OSD daemon cannot peer with any of the Ceph OSD daemons defined in its Ceph configuration file or the cluster map, it will ping a Ceph Monitor for the most recent copy of the cluster map every 30 seconds. You can change the Ceph Monitor heartbeat interval by adding the osd mon heartbeat interval setting under the [osd] section of the Ceph configuration file, or by setting the value at runtime.

Report Peering Failure

7.6. OSD reporting status

If an Ceph OSD Daemon does not report to a Ceph Monitor, the Ceph Monitor will consider the Ceph OSD Daemon down after the mon osd report timeout elapses. A Ceph OSD Daemon sends a report to a Ceph Monitor when a reportable event such as a failure, a change in placement group stats, a change in up_thru or when it boots within 5 seconds. You can change the Ceph OSD Daemon minimum report interval by adding the osd mon report interval min setting under the [osd] section of the Ceph configuration file, or by setting the value at runtime.

A Ceph OSD Daemon sends a report to a Ceph Monitor every 120 seconds irrespective of whether any notable changes occur. You can change the Ceph Monitor report interval by adding the osd mon report interval max setting under the [osd] section of the Ceph configuration file, or by setting the value at runtime.

110 Ceph Configuration updates 0720 10

7.7. Additional Resources

  • See all the Red Hat Ceph Storage Ceph Monitor and OSD configuration options in Appendix G for specific option descriptions and usage.

Chapter 8. Ceph debugging and logging configuration

As a storage administrator, you can increase the amount of debugging and logging information to help diagnose problems with the Red Hat Ceph Storage.

8.1. Prerequisites

  • Installation of the Red Hat Ceph Storage software.

8.2. Ceph debugging and logging

Debug settings are NOT required in the Ceph configuration file, but can be added to optimize logging. Changes to the Ceph logging configuration usually occur at runtime when a problem occurs, but may also be modified in the Ceph configuration file. For example, if there are issues when starting the cluster, consider increasing log settings in the Ceph configuration file. When the problem is resolved, remove the settings or restore them to optimal settings for runtime operations.

By default, view Ceph log files under /var/log/ceph.

Tip

When debug output slows down the cluster, the latency can hide race conditions.

Logging is resource intensive. If there is a problem in a specific area of the cluster, enable logging for that area of the cluster. For example, if OSDs are running fine but Ceph Object Gateways are not, start by enabling debug logging for the specific gateway instances encountering problems. Increase or decrease logging for each subsystem as needed.

Important

Verbose logging can generate over 1GB of data per hour. If the OS disk reaches its capacity, the node will stop working.

If Ceph logging is enabled or the rate of logging increased, ensure that the OS disk has sufficient capacity.

When the cluster is running well, remove unnecessary debugging settings to ensure the cluster runs optimally. Logging debug output messages is relatively slow, and a waste of resources when operating your cluster.

8.3. Additional Resources

  • See all the Red Hat Ceph Storage Ceph debugging and logging configuration options in Appendix J for specific option descriptions and usage.

Appendix A. General configuration options

These are the general configuration options for Ceph.

Note

Typically, these will be set automatically by deployment tools, such as Ansible.

fsid
Description
The file system ID. One per cluster.
Type
UUID
Required
No.
Default
N/A. Usually generated by deployment tools.
admin_socket
Description
The socket for executing administrative commands on a daemon, irrespective of whether Ceph monitors have established a quorum.
Type
String
Required
No
Default
/var/run/ceph/$cluster-$name.asok
pid_file
Description
The file in which the monitor or OSD will write its PID. For instance, /var/run/$cluster/$type.$id.pid will create /var/run/ceph/mon.a.pid for the mon with id a running in the ceph cluster. The pid file is removed when the daemon stops gracefully. If the process is not daemonized (meaning it runs with the -f or -d option), the pid file is not created.
Type
String
Required
No
Default
No
chdir
Description
The directory Ceph daemons change to once they are up and running. Default / directory recommended.
Type
String
Required
No
Default
/
max_open_files
Description
If set, when the Red Hat Ceph Storage cluster starts, Ceph sets the max_open_fds at the OS level (that is, the max # of file descriptors). It helps prevents Ceph OSDs from running out of file descriptors.
Type
64-bit Integer
Required
No
Default
0
fatal_signal_handlers
Description
If set, we will install signal handlers for SEGV, ABRT, BUS, ILL, FPE, XCPU, XFSZ, SYS signals to generate a useful log message.
Type
Boolean
Default
true

Appendix B. Ceph network configuration options

These are the common network configuration options for Ceph.

public_network
Description
The IP address and netmask of the public (front-side) network (for example, 192.168.0.0/24). Set in [global]. You can specify comma-delimited subnets.
Type
<ip-address>/<netmask> [, <ip-address>/<netmask>]
Required
No
Default
N/A
public_addr
Description
The IP address for the public (front-side) network. Set for each daemon.
Type
IP Address
Required
No
Default
N/A
cluster_network
Description
The IP address and netmask of the cluster network (for example, 10.0.0.0/24). Set in [global]. You can specify comma-delimited subnets.
Type
<ip-address>/<netmask> [, <ip-address>/<netmask>]
Required
No
Default
N/A
cluster_addr
Description
The IP address for the cluster network. Set for each daemon.
Type
Address
Required
No
Default
N/A
ms_type
Description
The messenger type for the network transport layer. Red Hat supports the simple and the async messenger type using posix semantics.
Type
String.
Required
No.
Default
async+posix
ms_public_type
Description
The messenger type for the network transport layer of the public network. It operates identically to ms_type, but is applicable only to the public or front-side network. This setting enables Ceph to use a different messenger type for the public or front-side and cluster or back-side networks.
Type
String.
Required
No.
Default
None.
ms_cluster_type
Description
The messenger type for the network transport layer of the cluster network. It operates identically to ms_type, but is applicable only to the cluster or back-side network. This setting enables Ceph to use a different messenger type for the public or front-side and cluster or back-side networks.
Type
String.
Required
No.
Default
None.

Host options

You must declare at least one Ceph Monitor in the Ceph configuration file, with a mon addr setting under each declared monitor. Ceph expects a host setting under each declared monitor, metadata server and OSD in the Ceph configuration file.

Important

Do not use localhost. Use the short name of the node, not the fully-qualified domain name (FQDN). Do not specify any value for host when using a third party deployment system that retrieves the node name for you.

mon_addr
Description
A list of <hostname>:<port> entries that clients can use to connect to a Ceph monitor. If not set, Ceph searches [mon.*] sections.
Type
String
Required
No
Default
N/A
host
Description
The host name. Use this setting for specific daemon instances (for example, [osd.0]).
Type
String
Required
Yes, for daemon instances.
Default
localhost

TCP options

Ceph disables TCP buffering by default.

ms_tcp_nodelay
Description
Ceph enables ms_tcp_nodelay so that each request is sent immediately (no buffering). Disabling Nagle’s algorithm increases network traffic, which can introduce congestion. If you experience large numbers of small packets, you may try disabling ms_tcp_nodelay, but be aware that disabling it will generally increase latency.
Type
Boolean
Required
No
Default
true
ms_tcp_rcvbuf
Description
The size of the socket buffer on the receiving end of a network connection. Disabled by default.
Type
32-bit Integer
Required
No
Default
0
ms_tcp_read_timeout
Description
If a client or daemon makes a request to another Ceph daemon and does not drop an unused connection, the tcp read timeout defines the connection as idle after the specified number of seconds.
Type
Unsigned 64-bit Integer
Required
No
Default
900 15 minutes.

Bind options

The bind options configure the default port ranges for the Ceph OSD daemons. The default range is 6800:7100. You can also enable Ceph daemons to bind to IPv6 addresses.

Important

Verify that the firewall configuration allows you to use the configured port range.

ms_bind_port_min
Description
The minimum port number to which an OSD daemon will bind.
Type
32-bit Integer
Default
6800
Required
No
ms_bind_port_max
Description
The maximum port number to which an OSD daemon will bind.
Type
32-bit Integer
Default
7300
Required
No.
ms_bind_ipv6
Description
Enables Ceph daemons to bind to IPv6 addresses.
Type
Boolean
Default
false
Required
No

Asynchronous messenger options

These Ceph messenger options configure the behavior of AsyncMessenger.

ms_async_transport_type
Description
Transport type used by the AsyncMessenger. Red Hat supports the posix setting, but does not support the dpdk or rdma settings at this time. POSIX uses standard TCP/IP networking and is the default value. Other transport types are experimental and are NOT supported.
Type
String
Required
No
Default
posix
ms_async_op_threads
Description
Initial number of worker threads used by each AsyncMessenger instance. This configuration setting SHOULD equal the number of replicas or erasure code chunks, but it may be set lower if the CPU core count is low or the number of OSDs on a single server is high.
Type
64-bit Unsigned Integer
Required
No
Default
3
ms_async_max_op_threads
Description
The maximum number of worker threads used by each AsyncMessenger instance. Set to lower values if the OSD host has limited CPU count, and increase if Ceph is underutilizing CPUs are underutilized.
Type
64-bit Unsigned Integer
Required
No
Default
5
ms_async_set_affinity
Description
Set to true to bind AsyncMessenger workers to particular CPU cores.
Type
Boolean
Required
No
Default
true
ms_async_affinity_cores
Description
When ms_async_set_affinity is true, this string specifies how AsyncMessenger workers are bound to CPU cores. For example, 0,2 will bind workers #1 and #2 to CPU cores #0 and #2, respectively. NOTE: When manually setting affinity, make sure to not assign workers to virtual CPUs created as an effect of hyper threading or similar technology, because they are slower than physical CPU cores.
Type
String
Required
No
Default
(empty)
ms_async_send_inline
Description
Send messages directly from the thread that generated them instead of queuing and sending from the AsyncMessenger thread. This option is known to decrease performance on systems with a lot of CPU cores, so it’s disabled by default.
Type
Boolean
Required
No
Default
false

Appendix C. Ceph Monitor configuration options

The following are Ceph monitor configuration options that can be set up during deployment.

mon_initial_members
Description
The IDs of initial monitors in a cluster during startup. If specified, Ceph requires an odd number of monitors to form an initial quorum (for example, 3).
Type
String
Default
None
mon_force_quorum_join
Description
Force monitor to join quorum even if it has been previously removed from the map
Type
Boolean
Default
False
mon_dns_srv_name
Description
The service name used for querying the DNS for the monitor hosts/addresses.
Type
String
Default
ceph-mon
fsid
Description
The cluster ID. One per cluster.
Type
UUID
Required
Yes.
Default
N/A. May be generated by a deployment tool if not specified.
mon_data
Description
The monitor’s data location.
Type
String
Default
/var/lib/ceph/mon/$cluster-$id
mon_data_size_warn
Description
Ceph issues a HEALTH_WARN status in the cluster log when the monitor’s data store reaches this threshold. The default value is 15GB.
Type
Integer
Default
15*1024*1024*1024*`
mon_data_avail_warn
Description
Ceph issues a HEALTH_WARN status in cluster log when the available disk space of the monitor’s data store is lower than or equal to this percentage.
Type
Integer
Default
30
mon_data_avail_crit
Description
Ceph issues a HEALTH_ERR status in cluster log when the available disk space of the monitor’s data store is lower or equal to this percentage.
Type
Integer
Default
5
mon_warn_on_cache_pools_without_hit_sets
Description
Ceph issues a HEALTH_WARN status in cluster log if a cache pool does not have the hit_set_type paramater set.
Type
Boolean
Default
True
mon_warn_on_crush_straw_calc_version_zero
Description
Ceph issues a HEALTH_WARN status in the cluster log if the CRUSH’s straw_calc_version is zero. See CRUSH tunables for details.
Type
Boolean
Default
True
mon_warn_on_legacy_crush_tunables
Description
Ceph issues a HEALTH_WARN status in the cluster log if CRUSH tunables are too old (older than mon_min_crush_required_version).
Type
Boolean
Default
True
mon_crush_min_required_version
Description
This setting defines the minimum tunable profile version required by the cluster.
Type
String
Default
firefly
mon_warn_on_osd_down_out_interval_zero
Description
Ceph issues a HEALTH_WARN status in the cluster log if the mon_osd_down_out_interval setting is zero, because the Leader behaves in a similar manner when the noout flag is set. Administrators find it easier to troubleshoot a cluster by setting the noout flag. Ceph issues the warning to ensure administrators know that the setting is zero.
Type
Boolean
Default
True
mon_cache_target_full_warn_ratio
Description
Ceph issues a warning when between the ratio of cache_target_full and target_max_object.
Type
Float
Default
0.66
mon_health_data_update_interval
Description
How often (in seconds) a monitor in the quorum shares its health status with its peers. A negative number disables health updates.
Type
Float
Default
60
mon_health_to_clog
Description
This setting enable Ceph to send a health summary to the cluster log periodically.
Type
Boolean
Default
True
mon_health_to_clog_tick_interval
Description
How often (in seconds) the monitor sends a health summary to the cluster log. A non-positive number disables it. If the current health summary is empty or identical to the last time, the monitor will not send the status to the cluster log.
Type
Integer
Default
3600
mon_health_to_clog_interval
Description
How often (in seconds) the monitor sends a health summary to the cluster log. A non-positive number disables it. The monitor will always send the summary to cluster log.
Type
Integer
Default
60
mon_osd_full_ratio
Description
The percentage of disk space used before an OSD is considered full.
Type
Float:
Default
.95
mon_osd_nearfull_ratio
Description
The percentage of disk space used before an OSD is considered nearfull.
Type
Float
Default
.85
mon_sync_trim_timeout
Description, Type
Double
Default
30.0
mon_sync_heartbeat_timeout
Description, Type
Double
Default
30.0
mon_sync_heartbeat_interval
Description, Type
Double
Default
5.0
mon_sync_backoff_timeout
Description, Type
Double
Default
30.0
mon_sync_timeout
Description
Number of seconds the monitor will wait for the next update message from its sync provider before it gives up and bootstraps again.
Type
Double
Default
30.0
mon_sync_max_retries
Description, Type
Integer
Default
5
mon_sync_max_payload_size
Description
The maximum size for a sync payload (in bytes).
Type
32-bit Integer
Default
1045676
paxos_max_join_drift
Description
The maximum Paxos iterations before we must first sync the monitor data stores. When a monitor finds that its peer is too far ahead of it, it will first sync with data stores before moving on.
Type
Integer
Default
10
paxos_stash_full_interval
Description
How often (in commits) to stash a full copy of the PaxosService state. Current this setting only affects mds, mon, auth and mgr PaxosServices.
Type
Integer
Default
25
paxos_propose_interval
Description
Gather updates for this time interval before proposing a map update.
Type
Double
Default
1.0
paxos_min
Description
The minimum number of paxos states to keep around
Type
Integer
Default
500
paxos_min_wait
Description
The minimum amount of time to gather updates after a period of inactivity.
Type
Double
Default
0.05
paxos_trim_min
Description
Number of extra proposals tolerated before trimming
Type
Integer
Default
250
paxos_trim_max
Description
The maximum number of extra proposals to trim at a time
Type
Integer
Default
500
paxos_service_trim_min
Description
The minimum amount of versions to trigger a trim (0 disables it)
Type
Integer
Default
250
paxos_service_trim_max
Description
The maximum amount of versions to trim during a single proposal (0 disables it)
Type
Integer
Default
500
mon_max_log_epochs
Description
The maximum amount of log epochs to trim during a single proposal
Type
Integer
Default
500
mon_max_pgmap_epochs
Description
The maximum amount of pgmap epochs to trim during a single proposal
Type
Integer
Default
500
mon_mds_force_trim_to
Description
Force monitor to trim mdsmaps to this point (0 disables it. dangerous, use with care)
Type
Integer
Default
0
mon_osd_force_trim_to
Description
Force monitor to trim osdmaps to this point, even if there is PGs not clean at the specified epoch (0 disables it. dangerous, use with care)
Type
Integer
Default
0
mon_osd_cache_size
Description
The size of osdmaps cache, not to rely on underlying store’s cache
Type
Integer
Default
10
mon_election_timeout
Description
On election proposer, maximum waiting time for all ACKs in seconds.
Type
Float
Default
5
mon_lease
Description
The length (in seconds) of the lease on the monitor’s versions.
Type
Float
Default
5
mon_lease_renew_interval_factor
Description
mon lease * mon lease renew interval factor will be the interval for the Leader to renew the other monitor’s leases. The factor should be less than 1.0.
Type
Float
Default
0.6
mon_lease_ack_timeout_factor
Description
The Leader will wait mon lease * mon lease ack timeout factor for the Providers to acknowledge the lease extension.
Type
Float
Default
2.0
mon_accept_timeout_factor
Description
The Leader will wait mon lease * mon accept timeout factor for the Requesters to accept a Paxos update. It is also used during the Paxos recovery phase for similar purposes.
Type
Float
Default
2.0
mon_min_osdmap_epochs
Description
Minimum number of OSD map epochs to keep at all times.
Type
32-bit Integer
Default
500
mon_max_pgmap_epochs
Description
Maximum number of PG map epochs the monitor should keep.
Type
32-bit Integer
Default
500
mon_max_log_epochs
Description
Maximum number of Log epochs the monitor should keep.
Type
32-bit Integer
Default
500
clock_offset
Description
How much to offset the system clock. See Clock.cc for details.
Type
Double
Default
0
mon_tick_interval
Description
A monitor’s tick interval in seconds.
Type
32-bit Integer
Default
5
mon_clock_drift_allowed
Description
The clock drift in seconds allowed between monitors.
Type
Float
Default
.050
mon_clock_drift_warn_backoff
Description
Exponential backoff for clock drift warnings.
Type
Float
Default
5
mon_timecheck_interval
Description
The time check interval (clock drift check) in seconds for the leader.
Type
Float
Default
300.0
mon_timecheck_skew_interval
Description
The time check interval (clock drift check) in seconds when in the presence of a skew in seconds for the Leader.
Type
Float
Default
30.0
mon_max_osd
Description
The maximum number of OSDs allowed in the cluster.
Type
32-bit Integer
Default
10000
mon_globalid_prealloc
Description
The number of global IDs to pre-allocate for clients and daemons in the cluster.
Type
32-bit Integer
Default
100
mon_sync_fs_threshold
Description
Synchronize with the filesystem when writing the specified number of objects. Set it to 0 to disable it.
Type
32-bit Integer
Default
5
mon_subscribe_interval
Description
The refresh interval, in seconds, for subscriptions. The subscription mechanism enables obtaining the cluster maps and log information.
Type
Double
Default
300
mon_stat_smooth_intervals
Description
Ceph will smooth statistics over the last N PG maps.
Type
Integer
Default
2
mon_probe_timeout
Description
Number of seconds the monitor will wait to find peers before bootstrapping.
Type
Double
Default
2.0
mon_daemon_bytes
Description
The message memory cap for metadata server and OSD messages (in bytes).
Type
64-bit Integer Unsigned
Default
400ul << 20
mon_max_log_entries_per_event
Description
The maximum number of log entries per event.
Type
Integer
Default
4096
mon_osd_prime_pg_temp
Description
Enables or disable priming the PGMap with the previous OSDs when an out OSD comes back into the cluster. With the true setting the clients will continue to use the previous OSDs until the newly in OSDs as that PG peered.
Type
Boolean
Default
true
mon_osd_prime_pg_temp_max_time
Description
How much time in seconds the monitor should spend trying to prime the PGMap when an out OSD comes back into the cluster.
Type
Float
Default
0.5
mon_osd_prime_pg_temp_max_time_estimate
Description
Maximum estimate of time spent on each PG before we prime all PGs in parallel.
Type
Float
Default
0.25
mon_osd_allow_primary_affinity
Description
allow primary_affinity to be set in the osdmap.
Type
Boolean
Default
False
mon_osd_pool_ec_fast_read
Description
Whether turn on fast read on the pool or not. It will be used as the default setting of newly created erasure pools if fast_read is not specified at create time.
Type
Boolean
Default
False
mon_mds_skip_sanity
Description
Skip safety assertions on FSMap, in case of bugs where we want to continue anyway. Monitor terminates if the FSMap sanity check fails, but we can disable it by enabling this option.
Type
Boolean
Default
False
mon_max_mdsmap_epochs
Description
The maximum amount of mdsmap epochs to trim during a single proposal.
Type
Integer
Default
500
mon_config_key_max_entry_size
Description
The maximum size of config-key entry (in bytes).
Type
Integer
Default
4096
mon_scrub_interval
Description
How often, in seconds, the monitor scrub its store by comparing the stored checksums with the computed ones of all the stored keys.
Type
Integer
Default
3600*24
mon_scrub_max_keys
Description
The maximum number of keys to scrub each time.
Type
Integer
Default
100
mon_compact_on_start
Description
Compact the database used as Ceph Monitor store on ceph-mon start. A manual compaction helps to shrink the monitor database and improve the performance of it if the regular compaction fails to work.
Type
Boolean
Default
False
mon_compact_on_bootstrap
Description
Compact the database used as Ceph Monitor store on on bootstrap. Monitor starts probing each other for creating a quorum after bootstrap. If it times out before joining the quorum, it will start over and bootstrap itself again.
Type
Boolean
Default
False
mon_compact_on_trim
Description
Compact a certain prefix (including paxos) when we trim its old states.
Type
Boolean
Default
True
mon_cpu_threads
Description
Number of threads for performing CPU intensive work on monitor.
Type
Boolean
Default
True
mon_osd_mapping_pgs_per_chunk
Description
We calculate the mapping from placement group to OSDs in chunks. This option specifies the number of placement groups per chunk.
Type
Integer
Default
4096
mon_osd_max_split_count
Description
Largest number of PGs per "involved" OSD to let split create. When we increase the pg_num of a pool, the placement groups will be splitted on all OSDs serving that pool. We want to avoid extreme multipliers on PG splits.
Type
Integer
Default
300
mon_session_timeout
Description
Monitor will terminate inactive sessions stay idle over this time limit.
Type
Integer
Default
300

Additional Resources

Appendix D. Cephx configuration options

The following are Cephx configuration options that can be set up during deployment.

auth_cluster_required
Description
If enabled, the Red Hat Ceph Storage cluster daemons, ceph-mon and ceph-osd, must authenticate with each other. Valid settings are cephx or none.
Type
String
Required
No
Default
cephx.
auth_service_required
Description
If enabled, the Red Hat Ceph Storage cluster daemons require Ceph clients to authenticate with the Red Hat Ceph Storage cluster in order to access Ceph services. Valid settings are cephx or none.
Type
String
Required
No
Default
cephx.
auth_client_required
Description
If enabled, the Ceph client requires the Red Hat Ceph Storage cluster to authenticate with the Ceph client. Valid settings are cephx or none.
Type
String
Required
No
Default
cephx.
keyring
Description
The path to the keyring file.
Type
String
Required
No
Default
/etc/ceph/$cluster.$name.keyring,/etc/ceph/$cluster.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin
keyfile
Description
The path to a key file (that is. a file containing only the key).
Type
String
Required
No
Default
None
key
Description
The key (that is, the text string of the key itself). Not recommended.
Type
String
Required
No
Default
None
ceph-mon
Location
$mon_data/keyring
Capabilities
mon 'allow *'
ceph-osd
Location
$osd_data/keyring
Capabilities
mon 'allow profile osd' osd 'allow *'
radosgw
Location
$rgw_data/keyring
Capabilities
mon 'allow rwx' osd 'allow rwx'
cephx_require_signatures
Description
If set to true, Ceph requires signatures on all message traffic between the Ceph client and the Red Hat Ceph Storage cluster, and between daemons comprising the Red Hat Ceph Storage cluster.
Type
Boolean
Required
No
Default
false
cephx_cluster_require_signatures
Description
If set to true, Ceph requires signatures on all message traffic between Ceph daemons comprising the Red Hat Ceph Storage cluster.
Type
Boolean
Required
No
Default
false
cephx_service_require_signatures
Description
If set to true, Ceph requires signatures on all message traffic between Ceph clients and the Red Hat Ceph Storage cluster.
Type
Boolean
Required
No
Default
false
cephx_sign_messages
Description
If the Ceph version supports message signing, Ceph will sign all messages so they cannot be spoofed.
Type
Boolean
Default
true
auth_service_ticket_ttl
Description
When the Red Hat Ceph Storage cluster sends a Ceph client a ticket for authentication, the cluster assigns the ticket a time to live.
Type
Double
Default
60*60

Additional Resources

  • <additional resource 1>
  • <additional resource 2>

Appendix E. Pools, placement groups and CRUSH configuration options

The Ceph options that govern pools, placement groups, and the CRUSH algorithm.

mon_allow_pool_delete
Description
Allows a monitor to delete a pool. In RHCS 3 and later releases, the monitor cannot delete the pool by default as an added measure to protect data.
Type
Boolean
Default
false
mon_max_pool_pg_num
Description
The maximum number of placement groups per pool.
Type
Integer
Default
65536
mon_pg_create_interval
Description
Number of seconds between PG creation in the same Ceph OSD Daemon.
Type
Float
Default
30.0
mon_pg_stuck_threshold
Description
Number of seconds after which PGs can be considered as being stuck.
Type
32-bit Integer
Default
300
mon_pg_min_inactive
Description
Ceph issues a HEALTH_ERR status in the cluster log if the number of PGs that remain inactive longer than the mon_pg_stuck_threshold exceeds this setting. The default setting is one PG. A non-positive number disables this setting.
Type
Integer
Default
1
mon_pg_warn_min_per_osd
Description
Ceph issues a HEALTH_WARN status in the cluster log if the average number of PGs per OSD in the cluster is less than this setting. A non-positive number disables this setting.
Type
Integer
Default
30
mon_pg_warn_max_per_osd
Description
Ceph issues a HEALTH_WARN status in the cluster log if the average number of PGs per OSD in the cluster is greater than this setting. A non-positive number disables this setting.
Type
Integer
Default
300
mon_pg_warn_min_objects
Description
Do not warn if the total number of objects in the cluster is below this number.
Type
Integer
Default
1000
mon_pg_warn_min_pool_objects
Description
Do not warn on pools whose object number is below this number.
Type
Integer
Default
1000
mon_pg_check_down_all_threshold
Description
The threshold of down OSDs by percentage after which Ceph checks all PGs to ensure they are not stuck or stale.
Type
Float
Default
0.5
mon_pg_warn_max_object_skew
Description
Ceph issue a HEALTH_WARN status in the cluster log if the average number of objects in a pool is greater than mon pg warn max object skew times the average number of objects for all pools. A non-positive number disables this setting.
Type
Float
Default
10
mon_delta_reset_interval
Description
The number of seconds of inactivity before Ceph resets the PG delta to zero. Ceph keeps track of the delta of the used space for each pool to aid administrators in evaluating the progress of recovery and performance.
Type
Integer
Default
10
mon_osd_max_op_age
Description
The maximimum age in seconds for an operation to complete before issuing a HEALTH_WARN status.
Type
Float
Default
32.0
osd_pg_bits
Description
Placement group bits per Ceph OSD Daemon.
Type
32-bit Integer
Default
6
osd_pgp_bits
Description
The number of bits per Ceph OSD Daemon for Placement Groups for Placement purpose (PGPs).
Type
32-bit Integer
Default
6
osd_crush_chooseleaf_type
Description
The bucket type to use for chooseleaf in a CRUSH rule. Uses ordinal rank rather than name.
Type
32-bit Integer
Default
1. Typically a host containing one or more Ceph OSD Daemons.
osd_pool_default_crush_replicated_ruleset
Description
The default CRUSH ruleset to use when creating a replicated pool.
Type
8-bit Integer
Default
0
osd_pool_erasure_code_stripe_unit
Description
Sets the default size, in bytes, of a chunk of an object stripe for erasure coded pools. Every object of size S will be stored as N stripes, with each data chunk receiving stripe unit bytes. Each stripe of N * stripe unit bytes will be encoded/decoded individually. This option can is overridden by the stripe_unit setting in an erasure code profile.
Type
Unsigned 32-bit Integer
Default
4096
osd_pool_default_size
Description
Sets the number of replicas for objects in the pool. The default value is the same as ceph osd pool set {pool-name} size {size}.
Type
32-bit Integer
Default
3
osd_pool_default_min_size
Description
Sets the minimum number of written replicas for objects in the pool in order to acknowledge a write operation to the client. If minimum is not met, Ceph will not acknowledge the write to the client. This setting ensures a minimum number of replicas when operating in degraded mode.
Type
32-bit Integer
Default
0, which means no particular minimum. If 0, minimum is size - (size / 2).
osd_pool_default_pg_num
Description
The default number of placement groups for a pool. The default value is the same as pg_num with mkpool.
Type
32-bit Integer
Default
8
osd_pool_default_pgp_num
Description
The default number of placement groups for placement for a pool. The default value is the same as pgp_num with mkpool. PG and PGP should be equal.
Type
32-bit Integer
Default
8
osd_pool_default_flags
Description
The default flags for new pools.
Type
32-bit Integer
Default
0
osd_max_pgls
Description
The maximum number of placement groups to list. A client requesting a large number can tie up the Ceph OSD Daemon.
Type
Unsigned 64-bit Integer
Default
1024
Note
Default should be fine.
osd_min_pg_log_entries
Description
The minimum number of placement group logs to maintain when trimming log files.
Type
32-bit Int Unsigned
Default
1000
osd_default_data_pool_replay_window
Description
The time, in seconds, for an OSD to wait for a client to replay a request.
Type
32-bit Integer
Default
45

Appendix F. Object Storage Daemon (OSD) configuration options

The following are Ceph Object Storage Daemon (OSD) configuration options which can be set during deployment.

osd_uuid
Description
The universally unique identifier (UUID) for the Ceph OSD.
Type
UUID
Default
The UUID.
Note
The osd uuid applies to a single Ceph OSD. The fsid applies to the entire cluster.
osd_data
Description

The path to the OSD’s data. You must create the directory when deploying Ceph. Mount a drive for OSD data at this mount point.

IMPORTANT: Red Hat does not recommend changing the default.
Type
String
Default
/var/lib/ceph/osd/$cluster-$id
osd_max_write_size
Description
The maximum size of a write in megabytes.
Type
32-bit Integer
Default
90
osd_client_message_size_cap
Description
The largest client data message allowed in memory.
Type
64-bit Integer Unsigned
Default
500MB default. 500*1024L*1024L
osd_class_dir
Description
The class path for RADOS class plug-ins.
Type
String
Default
$libdir/rados-classes
osd_max_scrubs
Description
The maximum number of simultaneous scrub operations for a Ceph OSD.
Type
32-bit Int
Default
1
osd_scrub_thread_timeout
Description
The maximum time in seconds before timing out a scrub thread.
Type
32-bit Integer
Default
60
osd_scrub_finalize_thread_timeout
Description
The maximum time in seconds before timing out a scrub finalize thread.
Type
32-bit Integer
Default
60*10
osd_scrub_begin_hour
Description
The earliest hour that light or deep scrubbing can begin. It is used with the osd scrub end hour parameter to define a scrubbing time window and allows constraining scrubbing to off-peak hours. The setting takes an integer to specify the hour on the 24-hour cycle where 0 represents the hour from 12:01 a.m. to 1:00 a.m., 13 represents the hour from 1:01 p.m. to 2:00 p.m., and so on.
Type
32-bit Integer
Default
0 for 12:01 to 1:00 a.m.
osd_scrub_end_hour
Description
The latest hour that light or deep scrubbing can begin. It is used with the osd scrub begin hour parameter to define a scrubbing time window and allows constraining scrubbing to off-peak hours. The setting takes an integer to specify the hour on the 24-hour cycle where 0 represents the hour from 12:01 a.m. to 1:00 a.m., 13 represents the hour from 1:01 p.m. to 2:00 p.m., and so on. The end hour must be greater than the begin hour.
Type
32-bit Integer
Default
24 for 11:01 p.m. to 12:00 a.m.
osd_scrub_load_threshold
Description
The maximum load. Ceph will not scrub when the system load (as defined by the getloadavg() function) is higher than this number. Default is 0.5.
Type
Float
Default
0.5
osd_scrub_min_interval
Description
The minimum interval in seconds for scrubbing the Ceph OSD when the Red Hat Ceph Storage cluster load is low.
Type
Float
Default
Once per day. 60*60*24
osd_scrub_max_interval
Description
The maximum interval in seconds for scrubbing the Ceph OSD irrespective of cluster load.
Type
Float
Default
Once per week. 7*60*60*24
osd_scrub_interval_randomize_ratio
Description
Takes the ratio and randomizes the scheduled scrub between osd scrub min interval and osd scrub max interval.
Type
Float
Default
0.5.
mon_warn_not_scrubbed
Description
Number of seconds after osd_scrub_interval to warn about any PGs that were not scrubbed.
Type
Integer
Default
0 (no warning).
osd_scrub_chunk_min
Description
The object store is partitioned into chunks which end on hash boundaries. For chunky scrubs, Ceph scrubs objects one chunk at a time with writes blocked for that chunk. The osd scrub chunk min setting represents minimum number of chunks to scrub.
Type
32-bit Integer
Default
5
osd_scrub_chunk_max
Description
The maximum number of chunks to scrub.
Type
32-bit Integer
Default
25
osd_scrub_sleep
Description
The time to sleep between deep scrub operations.
Type
Float
Default
0 (or off).
osd_scrub_during_recovery
Description
Allows scrubbing during recovery.
Type
Bool
Default
false
osd_scrub_invalid_stats
Description
Forces extra scrub to fix stats marked as invalid.
Type
Bool
Default
true
osd_scrub_priority
Description
Controls queue priority of scrub operations versus client I/O.
Type
Unsigned 32-bit Integer
Default
5
osd_scrub_cost
Description
Cost of scrub operations in megabytes for queue scheduling purposes.
Type
Unsigned 32-bit Integer
Default
50 << 20
osd_deep_scrub_interval
Description
The interval for deep scrubbing, that is fully reading all data. The osd scrub load threshold parameter does not affect this setting.
Type
Float
Default
Once per week. 60*60*24*7
osd_deep_scrub_stride
Description
Read size when doing a deep scrub.
Type
32-bit Integer
Default
512 KB. 524288
mon_warn_not_deep_scrubbed
Description
Number of seconds after osd_deep_scrub_interval to warn about any PGs that were not scrubbed.
Type
Integer
Default
0 (no warning).
osd_deep_scrub_randomize_ratio
Description
The rate at which scrubs will randomly become deep scrubs (even before osd_deep_scrub_interval has past).
Type
Float
Default
0.15 or 15%.
osd_deep_scrub_update_digest_min_age
Description
How many seconds old objects must be before scrub updates the whole-object digest.
Type
Integer
Default
120 (2 hours).
osd_op_num_shards
Description
The number of shards for client operations.
Type
32-bit Integer
Default
0
osd_op_num_threads_per_shard
Description
The number of threads per shard for client operations.
Type
32-bit Integer
Default
0
osd_op_num_shards_hdd
Description
The number of shards for HDD operations.
Type
32-bit Integer
Default
5
osd_op_num_threads_per_shard_hdd
Description
The number of threads per shard for HDD operations.
Type
32-bit Integer
Default
1
osd_op_num_shards_ssd
Description
The number of shards for SSD operations.
Type
32-bit Integer
Default
8
osd_op_num_threads_per_shard_ssd
Description
The number of threads per shard for SSD operations.
Type
32-bit Integer
Default
2
osd_client_op_priority
Description
The priority set for client operations. It is relative to osd recovery op priority.
Type
32-bit Integer
Default
63
Valid Range
1-63
osd_recovery_op_priority
Description
The priority set for recovery operations. It is relative to osd client op priority.
Type
32-bit Integer
Default
3
Valid Range
1-63
osd_op_thread_timeout
Description
The Ceph OSD operation thread timeout in seconds.
Type
32-bit Integer
Default
30
osd_op_complaint_time
Description
An operation becomes complaint worthy after the specified number of seconds have elapsed.
Type
Float
Default
30
osd_disk_threads
Description
The number of disk threads, which are used to perform background disk intensive OSD operations such as scrubbing and snap trimming.
Type
32-bit Integer
Default
1
osd_disk_thread_ioprio_class
Description

Sets the ioprio_set(2) I/O scheduling class for the disk thread. Acceptable values are:

  • idle
  • be
  • rt + The idle class means the disk thread will have lower priority than any other thread in the OSD. This is useful to slow down scrubbing on an OSD that is busy handling client operations. + The be class is the default and is the same priority as all other threads in the OSD. + The rt class means the disk thread will have precedence over all other threads in the OSD. This is useful if scrubbing is much needed and must make progress at the expense of client operations.
Type
String
Default
an empty string
osd_disk_thread_ioprio_priority
Description
It sets the ioprio_set(2) I/O scheduling priority of the disk thread ranging from 0 (highest) to 7 (lowest). If all OSDs on a given host were in class idle and compete for I/O due to controller congestion, it can be used to lower the disk thread priority of one OSD to 7 so that another OSD with priority 0 can potentially scrub faster. +
Type
Integer in the range of 0 to 7 or -1 if not to be used.
Default
-1
Important

The osd disk thread ioprio class and osd disk thread ioprio priority options will only be used if both are set to a non default value. In addition, it only works with the Linux Kernel CFQ scheduler.

osd_op_history_size
Description
The maximum number of completed operations to track.
Type
32-bit Unsigned Integer
Default
20
osd_op_history_duration
Description
The oldest completed operation to track.
Type
32-bit Unsigned Integer
Default
600
osd_op_log_threshold
Description
How many operations logs to display at once.
Type
32-bit Integer
Default
5
osd_op_timeout
Description
The time in seconds after which running OSD operations time out.
Type
Integer
Default
0
Important

Do not set the osd op timeout option unless your clients can handle the consequences. For example, setting this parameter on clients running in virtual machines can lead to data corruption because the virtual machines interpret this timeout as a hardware failure.

osd_max_backfills
Description
The maximum number of backfill operations allowed to or from a single OSD.
Type
64-bit Unsigned Integer
Default
1
osd_backfill_scan_min
Description
The minimum number of objects per backfill scan.
Type
32-bit Integer
Default
64
osd_backfill_scan_max
Description
The maximum number of objects per backfill scan.
Type
32-bit Integer
Default
512
osd_backfill_full_ratio
Description
Refuse to accept backfill requests when the Ceph OSD’s full ratio is above this value.
Type
Float
Default
0.85
osd_backfill_retry_interval
Description
The number of seconds to wait before retrying backfill requests.
Type
Double
Default
10.0
osd_map_dedup
Description
Enable removing duplicates in the OSD map.
Type
Boolean
Default
true
osd_map_cache_size
Description
The size of the OSD map cache in megabytes.
Type
32-bit Integer
Default
50
osd_map_cache_bl_size
Description
The size of the in-memory OSD map cache in OSD daemons.
Type
32-bit Integer
Default
50
osd_map_cache_bl_inc_size
Description
The size of the in-memory OSD map cache incrementals in OSD daemons.
Type
32-bit Integer
Default
100
osd_map_message_max
Description
The maximum map entries allowed per MOSDMap message.
Type
32-bit Integer
Default
40
osd_snap_trim_thread_timeout
Description
The maximum time in seconds before timing out a snap trim thread.
Type
32-bit Integer
Default
60*60*1
osd_pg_max_concurrent_snap_trims
Description
The max number of parallel snap trims/PG. This controls how many objects per PG to trim at once.
Type
32-bit Integer
Default
2
osd_snap_trim_sleep
Description
Insert a sleep between every trim operation a PG issues.
Type
32-bit Integer
Default
0
osd_max_trimming_pgs
Description
The max number of trimming PGs
Type
32-bit Integer
Default
2
osd_backlog_thread_timeout
Description
The maximum time in seconds before timing out a backlog thread.
Type
32-bit Integer
Default
60*60*1
osd_default_notify_timeout
Description
The OSD default notification timeout (in seconds).
Type
32-bit Integer Unsigned
Default
30
osd_check_for_log_corruption
Description
Check log files for corruption. Can be computationally expensive.
Type
Boolean
Default
false
osd_remove_thread_timeout
Description
The maximum time in seconds before timing out a remove OSD thread.
Type
32-bit Integer
Default
60*60
osd_command_thread_timeout
Description
The maximum time in seconds before timing out a command thread.
Type
32-bit Integer
Default
10*60
osd_command_max_records
Description
Limits the number of lost objects to return.
Type
32-bit Integer
Default
256
osd_auto_upgrade_tmap
Description
Uses tmap for omap on old objects.
Type
Boolean
Default
true
osd_tmapput_sets_users_tmap
Description
Uses tmap for debugging only.
Type
Boolean
Default
false
osd_preserve_trimmed_log
Description
Preserves trimmed log files, but uses more disk space.
Type
Boolean
Default
false
osd_recovery_delay_start
Description
After peering completes, Ceph will delay for the specified number of seconds before starting to recover objects.
Type
Float
Default
0
osd_recovery_max_active
Description
The number of active recovery requests per OSD at one time. More requests will accelerate recovery, but the requests places an increased load on the cluster.
Type
32-bit Integer
Default
3
osd_recovery_max_chunk
Description
The maximum size of a recovered chunk of data to push.
Type
64-bit Integer Unsigned
Default
8 << 20
osd_recovery_threads
Description
The number of threads for recovering data.
Type
32-bit Integer
Default
1
osd_recovery_thread_timeout
Description
The maximum time in seconds before timing out a recovery thread.
Type
32-bit Integer
Default
30
osd_recover_clone_overlap
Description
Preserves clone overlap during recovery. Should always be set to true.
Type
Boolean
Default
true

Appendix G. Ceph Monitor and OSD configuration options

When modifying heartbeat settings, include them in the [global] section of the Ceph configuration file.

mon_osd_min_up_ratio
Description
The minimum ratio of up Ceph OSD Daemons before Ceph will mark Ceph OSD Daemons down.
Type
Double
Default
.3
mon_osd_min_in_ratio
Description
The minimum ratio of in Ceph OSD Daemons before Ceph will mark Ceph OSD Daemons out.
Type
Double
Default
.3
mon_osd_laggy_halflife
Description
The number of seconds laggy estimates will decay.
Type
Integer
Default
60*60
mon_osd_laggy_weight
Description
The weight for new samples in laggy estimation decay.
Type
Double
Default
0.3
mon_osd_laggy_max_interval
Description
Maximum value of laggy_interval in laggy estimations (in seconds). The monitor uses an adaptive approach to evaluate the laggy_interval of a certain OSD. This value will be used to calculate the grace time for that OSD.
Type
Integer
Default
300
mon_osd_adjust_heartbeat_grace
Description
If set to true, Ceph will scale based on laggy estimations.
Type
Boolean
Default
true
mon_osd_adjust_down_out_interval
Description
If set to true, Ceph will scaled based on laggy estimations.
Type
Boolean
Default
true
mon_osd_auto_mark_in
Description
Ceph will mark any booting Ceph OSD Daemons as in the Ceph Storage Cluster.
Type
Boolean
Default
false
mon_osd_auto_mark_auto_out_in
Description
Ceph will mark booting Ceph OSD Daemons auto marked out of the Ceph Storage Cluster as in the cluster.
Type
Boolean
Default
true
mon_osd_auto_mark_new_in
Description
Ceph will mark booting new Ceph OSD Daemons as in the Ceph Storage Cluster.
Type
Boolean
Default
true
mon_osd_down_out_interval
Description
The number of seconds Ceph waits before marking a Ceph OSD Daemon down and out if it does not respond.
Type
32-bit Integer
Default
300
mon_osd_downout_subtree_limit
Description
The largest CRUSH unit type that Ceph will automatically mark out.
Type
String
Default
rack
mon_osd_reporter_subtree_level
Description
This setting defines the parent CRUSH unit type for the reporting OSDs. The OSDs send failure reports to the monitor if they find an unresponsive peer. The monitor may mark the reported OSD down and then out after a grace period.
Type
String
Default
host
mon_osd_report_timeout
Description
The grace period in seconds before declaring unresponsive Ceph OSD Daemons down.
Type
32-bit Integer
Default
900
mon_osd_min_down_reporters
Description
The minimum number of Ceph OSD Daemons required to report a down Ceph OSD Daemon.
Type
32-bit Integer
Default
2
osd_heartbeat_address
Description
An Ceph OSD Daemon’s network address for heartbeats.
Type
Address
Default
The host address.
osd_heartbeat_interval
Description
How often an Ceph OSD Daemon pings its peers (in seconds).
Type
32-bit Integer
Default
6
osd_heartbeat_grace
Description
The elapsed time when a Ceph OSD Daemon has not shown a heartbeat that the Ceph Storage Cluster considers it down.
Type
32-bit Integer
Default
20
osd_mon_heartbeat_interval
Description
How often the Ceph OSD Daemon pings a Ceph Monitor if it has no Ceph OSD Daemon peers.
Type
32-bit Integer
Default
30
osd_mon_report_interval_max
Description
The maximum time in seconds that a Ceph OSD Daemon can wait before it must report to a Ceph Monitor.
Type
32-bit Integer
Default
120
osd_mon_report_interval_min
Description
The minimum number of seconds a Ceph OSD Daemon may wait from startup or another reportable event before reporting to a Ceph Monitor.
Type
32-bit Integer
Default
5
Valid Range
Should be less than osd mon report interval max
osd_mon_ack_timeout
Description
The number of seconds to wait for a Ceph Monitor to acknowledge a request for statistics.
Type
32-bit Integer
Default
30

Appendix H. Ceph debugging and logging configuration options

Logging and debugging settings are not required in a Ceph configuration file, but you can override default settings as needed.

The options take a single item that is assumed to be the default for all daemons regardless of channel. For example, specifying "info" is interpreted as "default=info". However, options can also take key/value pairs. For example, "default=daemon audit=local0" is interpreted as "default all to 'daemon', override 'audit' with 'local0'."

log_file
Description
The location of the logging file for the cluster.
Type
String
Required
No
Default
/var/log/ceph/$cluster-$name.log
mon_cluster_log_file
Description
The location of the monitor cluster’s log file.
Type
String
Required
No
Default
/var/log/ceph/$cluster.log
log_max_new
Description
The maximum number of new log files.
Type
Integer
Required
No
Default
1000
log_max_recent
Description
The maximum number of recent events to include in a log file.
Type
Integer
Required
No
Default
10000
log_flush_on_exit
Description
Determines if Ceph flushes the log files after exit.
Type
Boolean
Required
No
Default
true
mon_cluster_log_file_level
Description
The level of file logging for the monitor cluster. Valid settings include "debug", "info", "sec", "warn", and "error".
Type
String
Default
"info"
log_to_stderr
Description
Determines if logging messages appear in stderr.
Type
Boolean
Required
No
Default
true
err_to_stderr
Description
Determines if error messages appear in stderr.
Type
Boolean
Required
No
Default
true
log_to_syslog
Description
Determines if logging messages appear in syslog.
Type
Boolean
Required
No
Default
false
err_to_syslog
Description
Determines if error messages appear in syslog.
Type
Boolean
Required
No
Default
false
clog_to_syslog
Description
Determines if clog messages will be sent to syslog.
Type
Boolean
Required
No
Default
false
mon_cluster_log_to_syslog
Description
Determines if the cluster log will be output to syslog.
Type
Boolean
Required
No
Default
false
mon_cluster_log_to_syslog_level
Description
The level of syslog logging for the monitor cluster. Valid settings include "debug", "info", "sec", "warn", and "error".
Type
String
Default
"info"
mon_cluster_log_to_syslog_facility
Description
The facility generating the syslog output. This is usually set to "daemon" for the Ceph daemons.
Type
String
Default
"daemon"
clog_to_monitors
Description
Determines if clog messages will be sent to monitors.
Type
Boolean
Required
No
Default
true
mon_cluster_log_to_graylog
Description
Determines if the cluster will output log messages to graylog.
Type
String
Default
"false"
mon_cluster_log_to_graylog_host
Description
The IP address of the graylog host. If the graylog host is different from the monitor host, override this setting with the appropriate IP address.
Type
String
Default
"127.0.0.1"
mon_cluster_log_to_graylog_port
Description
Graylog logs will be sent to this port. Ensure the port is open for receiving data.
Type
String
Default
"12201"
osd_preserve_trimmed_log
Description
Preserves trimmed logs after trimming.
Type
Boolean
Required
No
Default
false
osd_tmapput_sets_uses_tmap
Description
Uses tmap. For debug only.
Type
Boolean
Required
No
Default
false
osd_min_pg_log_entries
Description
The minimum number of log entries for placement groups.
Type
32-bit Unsigned Integer
Required
No
Default
1000
osd_op_log_threshold
Description
How many op log messages to show up in one pass.
Type
Integer
Required
No
Default
5

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