Chapter 2. High Level Monitoring

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 on the command line, open a new terminal. Then, enter:

ceph -w

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

cluster b370a29d-9287-4ca3-ab57-3d824f65e339
 health HEALTH_OK
 monmap e1: 1 mons at {ceph1=10.0.0.8:6789/0}, election epoch 2, quorum 0 ceph1
 osdmap e63: 2 osds: 2 up, 2 in
  pgmap v41338: 952 pgs, 20 pools, 17130 MB data, 2199 objects
        115 GB used, 167 GB / 297 GB avail
             952 active+clean

2014-06-02 15:45:21.655871 osd.0 [INF] 17.71 deep-scrub ok
2014-06-02 15:45:47.880608 osd.1 [INF] 1.0 scrub ok
2014-06-02 15:45:48.865375 osd.1 [INF] 1.3 scrub ok
2014-06-02 15:45:50.866479 osd.1 [INF] 1.4 scrub ok
2014-06-02 15:45:01.345821 mon.0 [INF] pgmap v41339: 952 pgs: 952 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
2014-06-02 15:45:05.718640 mon.0 [INF] pgmap v41340: 952 pgs: 1 active+clean+scrubbing+deep, 951 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
2014-06-02 15:45:53.997726 osd.1 [INF] 1.5 scrub ok
2014-06-02 15:45:06.734270 mon.0 [INF] pgmap v41341: 952 pgs: 1 active+clean+scrubbing+deep, 951 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
2014-06-02 15:45:15.722456 mon.0 [INF] pgmap v41342: 952 pgs: 952 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail
2014-06-02 15:46:06.836430 osd.0 [INF] 17.75 deep-scrub ok
2014-06-02 15:45:55.720929 mon.0 [INF] pgmap v41343: 952 pgs: 1 active+clean+scrubbing+deep, 951 active+clean; 17130 MB data, 115 GB used, 167 GB / 297 GB avail

The output provides:

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

ceph df

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

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

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

ceph status

Or:

ceph -s

In interactive mode, type status and press Enter. :

ceph> status

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

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

If your cluster has multiple monitors (required for high availability production clusters), 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. If there is a problem with the monitor cluster that prevents agreement on the state of the cluster, the fault may prevent Ceph clients from reading and writing data.

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"}
           ]
    }
}

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.

Additionally, you can set configuration values at runtime directly (i.e., the admin socket bypasses the monitor, unlike ceph tell {daemon-type}.{id} injectargs, which relies on the monitor but doesn’t require you to login directly to the host in question ).

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

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

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

ceph osd stat

Or:

ceph osd dump

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

eNNNN: x osds: y up, z in

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

ceph osd tree

The output should look something like this:

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

If an OSD is down, connect to the node and start it. You can use Calamari to restart the node, or you can use the CLI. For example:

sudo /etc/init.d/ceph start osd.1