====================== Monitoring a Cluster ====================== 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. Interactive Mode ================ 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 Checking Cluster Health ======================= 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. Watching a 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 Checking a Cluster's Status =========================== 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} Checking OSD Status =================== 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`` in the cluster (you can read and write data) or it is out of the cluster ``out``. If it is ``down``, it should also be ``out``. If an OSD is ``down`` and ``in``, there is a problem. .. ditaa:: +----------------+ +----------------+ | | | | | OSD #n In | | OSD #n Up | | | | | +----------------+ +----------------+ ^ ^ | | | | v v +----------------+ +----------------+ | | | | | OSD #n Out | | OSD #n Down | | | | | +----------------+ +----------------+ 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 Checking Monitor Status ======================= 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: .. code-block:: javascript { "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"} ] } } Checking MDS Status =================== 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 Checking Placement Group States =============================== Placement groups map objects to OSDs. When you monitor your placement groups, you will want them to be ``active`` and ``clean``. For other PG states, see `Placement Group States`_. .. _Placement Group States: ../pg-states