Once you have a running cluster, you may use the ceph tool to monitor your cluster. Monitoring a cluster typically involves checking OSD status, monitor status, placement group status and metadata server status.
To run the ceph tool in interactive mode, type ceph at the command line with no arguments. For example:
ceph
ceph> health
ceph> status
ceph> quorum_status
ceph> mon_status
After you start your cluster, and before you start reading and/or writing data, check your cluster’s health first. You can check on the health of your Ceph cluster with the following:
ceph health
If you specified non-default locations for your configuration or keyring, you may specify their locations:
ceph -c /path/to/conf -k /path/to/keyring health
Upon starting the Ceph cluster, you will likely encounter a health warning such as HEALTH_WARN XXX num placement groups stale. Wait a few moments and check it again. When your cluster is ready, ceph health should return a message such as HEALTH_OK. At that point, it is okay to begin using the cluster.
To watch the cluster’s ongoing events, open a new terminal. Then, enter:
ceph -w
Ceph will print each version of the placement group map and their status. For example, a tiny Ceph cluster consisting of one monitor, one metadata server and two OSDs may print the following:
health HEALTH_OK
monmap e1: 1 mons at {a=192.168.0.1:6789/0}, election epoch 0, quorum 0 a
osdmap e13: 2 osds: 2 up, 2 in
placement groupmap v9713: 384 placement groups: 384 active+clean; 8730 bytes data, 22948 MB used, 264 GB / 302 GB avail
mdsmap e4: 1/1/1 up {0=a=up:active}
2012-08-01 11:33:53.831268 mon.0 [INF] placement groupmap v9712: 384 placement groups: 384 active+clean; 8730 bytes data, 22948 MB used, 264 GB / 302 GB avail
2012-08-01 11:35:31.904650 mon.0 [INF] placement groupmap v9713: 384 placement groups: 384 active+clean; 8730 bytes data, 22948 MB used, 264 GB / 302 GB avail
2012-08-01 11:35:53.903189 mon.0 [INF] placement groupmap v9714: 384 placement groups: 384 active+clean; 8730 bytes data, 22948 MB used, 264 GB / 302 GB avail
2012-08-01 11:37:31.865809 mon.0 [INF] placement groupmap v9715: 384 placement groups: 384 active+clean; 8730 bytes data, 22948 MB used, 264 GB / 302 GB avail
To check a cluster’s status, execute the following:
ceph status
Or:
ceph -s
In interactive mode, type status and press Enter.
ceph> status
Ceph will print the cluster status. For example, a tiny Ceph cluster consisting of one monitor, one metadata server and two OSDs may print the following:
health HEALTH_OK
monmap e1: 1 mons at {a=192.168.0.1:6789/0}, election epoch 0, quorum 0 a
osdmap e13: 2 osds: 2 up, 2 in
placement groupmap v9754: 384 placement groups: 384 active+clean; 8730 bytes data, 22948 MB used, 264 GB / 302 GB avail
mdsmap e4: 1/1/1 up {0=a=up:active}
You can check OSDs to ensure they are up and in by executing:
ceph osd stat
Or:
ceph osd dump
You can also check view OSDs according to their position in the CRUSH map.
ceph osd tree
Ceph will print out a CRUSH tree with a host, its OSDs, whether they are up and their weight.
# id weight type name up/down reweight
-1 3 pool default
-3 3 rack mainrack
-2 3 host osd-host
0 1 osd.0 up 1
1 1 osd.1 up 1
2 1 osd.2 up 1
For a detailed discussion, refer to Monitoring OSDs and Placement Groups.
If your cluster has multiple monitors (likely), you should check the monitor quorum status after you start the cluster before reading and/or writing data. A quorum must be present when multiple monitors are running. You should also check monitor status periodically to ensure that they are running.
To see display the monitor map, execute the following:
ceph mon stat
Or:
ceph mon dump
To check the quorum status for the monitor cluster, execute the following:
ceph quorum_status
Ceph will return the quorum status. For example, a Ceph cluster consisting of three monitors may return the following:
{ "election_epoch": 10,
"quorum": [
0,
1,
2],
"monmap": { "epoch": 1,
"fsid": "444b489c-4f16-4b75-83f0-cb8097468898",
"modified": "2011-12-12 13:28:27.505520",
"created": "2011-12-12 13:28:27.505520",
"mons": [
{ "rank": 0,
"name": "a",
"addr": "127.0.0.1:6789\/0"},
{ "rank": 1,
"name": "b",
"addr": "127.0.0.1:6790\/0"},
{ "rank": 2,
"name": "c",
"addr": "127.0.0.1:6791\/0"}
]
}
}
Metadata servers provide metadata services for Ceph FS. Metadata servers have two sets of states: up | down and active | inactive. To ensure your metadata servers are up and active, execute the following:
ceph mds stat
To display details of the metadata cluster, execute the following:
ceph mds dump
Placement groups map objects to OSDs. When you monitor your placement groups, you will want them to be active and clean. For a detailed discussion, refer to Monitoring OSDs and Placement Groups.
The Ceph admin socket allows you to query a daemon via a socket interface. By default, Ceph sockets reside under /var/run/ceph. To access a daemon via the admin socket, login to the host running the daemon and use the following command:
ceph --admin-daemon /var/run/ceph/{socket-name}
To view the available admin socket commands, execute the following command:
ceph --admin-daemon /var/run/ceph/{socket-name} help
The admin socket command enables you to show and set your configuration at runtime. See Viewing a Configuration at Runtime for details.
Additionally, you can set configuration values at runtime directly (i.e., the admin socket bypasses the monitor, unlike ceph {daemon-type} tell {id} injectargs, which relies on the monitor but doesn’t require you to login directly to the host in question ).