====================== 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 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: - Cluster ID - Cluster health status - The monitor map epoch and the status of the monitor quorum - The OSD map epoch and the status of OSDs - The placement group map version - The number of placement groups and pools - The *notional* amount of data stored and the number of objects stored; and, - The total amount of data stored. .. topic:: How Ceph Calculates Data Usage The ``used`` value reflects the *actual* amount of raw storage used. The ``xxx GB / xxx GB`` value means the amount available (the lesser number) of the overall storage capacity of the cluster. The notional number reflects the size of the stored data before it is replicated, cloned or snapshotted. Therefore, the amount of data actually stored typically exceeds the notional amount stored, because Ceph creates replicas of the data and may also use storage capacity for cloning and snapshotting. Checking a Cluster's Usage Stats ================================ 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. - **SIZE:** The overall storage capacity of the cluster. - **AVAIL:** The amount of free space available in the cluster. - **RAW USED:** The amount of raw storage used. - **% RAW USED:** The percentage of raw storage used. Use this number in conjunction with the ``full ratio`` and ``near full ratio`` to ensure that you are not reaching your cluster's capacity. See `Storage Capacity`_ for additional details. 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 2MB or more depending on the number of replicas, clones and snapshots. - **NAME:** The name of the pool. - **ID:** The pool ID. - **USED:** The notional amount of data stored in kilobytes, unless the number appends **M** for megabytes or **G** for gigabytes. - **%USED:** The notional percentage of storage used per pool. - **Objects:** The notional number of objects stored per pool. .. note:: The numbers in the **POOLS** section are notional. They are not inclusive of the number of replicas, shapshots or clones. As a result, the sum of the **USED** and **%USED** amounts will not add up to the **RAW USED** and **%RAW USED** amounts in the **GLOBAL** section of the output. 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, 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 Checking OSD Status =================== 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`_. 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 a detailed discussion, refer to `Monitoring OSDs and Placement Groups`_. .. _Monitoring OSDs and Placement Groups: ../monitoring-osd-pg Using the Admin Socket ====================== 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 tell {daemon-type}.{id} injectargs``, which relies on the monitor but doesn't require you to login directly to the host in question ). .. _Viewing a Configuration at Runtime: ../../configuration/ceph-conf#ceph-runtime-config .. _Storage Capacity: ../../configuration/mon-config-ref#storage-capacity