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352 lines
11 KiB
ReStructuredText
======================
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Monitoring a Cluster
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======================
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Once you have a running cluster, you may use the ``ceph`` tool to monitor your
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cluster. Monitoring a cluster typically involves checking OSD status, monitor
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status, placement group status and metadata server status.
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Using the command line
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======================
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Interactive mode
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----------------
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To run the ``ceph`` tool in interactive mode, type ``ceph`` at the command line
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with no arguments. For example::
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ceph
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ceph> health
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ceph> status
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ceph> quorum_status
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ceph> mon_status
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Non-default paths
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-----------------
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If you specified non-default locations for your configuration or keyring,
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you may specify their locations::
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ceph -c /path/to/conf -k /path/to/keyring health
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Checking a Cluster's Status
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===========================
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After you start your cluster, and before you start reading and/or
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writing data, check your cluster's status first.
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To check a cluster's status, execute the following::
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ceph status
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Or::
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ceph -s
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In interactive mode, type ``status`` and press **Enter**. ::
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ceph> status
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Ceph will print the cluster status. For example, a tiny Ceph demonstration
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cluster with one of each service may print the following:
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::
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cluster:
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id: 477e46f1-ae41-4e43-9c8f-72c918ab0a20
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health: HEALTH_OK
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services:
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mon: 1 daemons, quorum a
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mgr: x(active)
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mds: 1/1/1 up {0=a=up:active}
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osd: 1 osds: 1 up, 1 in
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data:
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pools: 2 pools, 16 pgs
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objects: 21 objects, 2246 bytes
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usage: 546 GB used, 384 GB / 931 GB avail
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pgs: 16 active+clean
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.. topic:: How Ceph Calculates Data Usage
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The ``usage`` value reflects the *actual* amount of raw storage used. The
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``xxx GB / xxx GB`` value means the amount available (the lesser number)
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of the overall storage capacity of the cluster. The notional number reflects
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the size of the stored data before it is replicated, cloned or snapshotted.
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Therefore, the amount of data actually stored typically exceeds the notional
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amount stored, because Ceph creates replicas of the data and may also use
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storage capacity for cloning and snapshotting.
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Watching a Cluster
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==================
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In addition to local logging by each daemon, Ceph clusters maintain
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a *cluster log* that records high level events about the whole system.
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This is logged to disk on monitor servers (as ``/var/log/ceph/ceph.log`` by
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default), but can also be monitored via the command line.
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To follow the cluster log, use the following command
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::
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ceph -w
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Ceph will print the status of the system, followed by each log message as it
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is emitted. For example:
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::
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cluster:
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id: 477e46f1-ae41-4e43-9c8f-72c918ab0a20
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health: HEALTH_OK
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services:
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mon: 1 daemons, quorum a
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mgr: x(active)
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mds: 1/1/1 up {0=a=up:active}
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osd: 1 osds: 1 up, 1 in
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data:
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pools: 2 pools, 16 pgs
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objects: 21 objects, 2246 bytes
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usage: 546 GB used, 384 GB / 931 GB avail
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pgs: 16 active+clean
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2017-07-24 08:15:11.329298 mon.a mon.0 172.21.9.34:6789/0 23 : cluster [INF] osd.0 172.21.9.34:6806/20527 boot
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2017-07-24 08:15:14.258143 mon.a mon.0 172.21.9.34:6789/0 39 : cluster [INF] Activating manager daemon x
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2017-07-24 08:15:15.446025 mon.a mon.0 172.21.9.34:6789/0 47 : cluster [INF] Manager daemon x is now available
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In addition to using ``ceph -w`` to print log lines as they are emitted,
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use ``ceph log last [n]`` to see the most recent ``n`` lines from the cluster
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log.
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Monitoring Health Checks
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========================
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Ceph continously runs various *health checks* against its own status. When
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a health check fails, this is reflected in the output of ``ceph status`` (or
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``ceph health``). In addition, messages are sent to the cluster log to
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indicate when a check fails, and when the cluster recovers.
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For example, when an OSD goes down, the ``health`` section of the status
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output may be updated as follows:
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::
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health: HEALTH_WARN
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1 osds down
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Degraded data redundancy: 21/63 objects degraded (33.333%), 16 pgs unclean, 16 pgs degraded
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At this time, cluster log messages are also emitted to record the failure of the
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health checks:
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::
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2017-07-25 10:08:58.265945 mon.a mon.0 172.21.9.34:6789/0 91 : cluster [WRN] Health check failed: 1 osds down (OSD_DOWN)
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2017-07-25 10:09:01.302624 mon.a mon.0 172.21.9.34:6789/0 94 : cluster [WRN] Health check failed: Degraded data redundancy: 21/63 objects degraded (33.333%), 16 pgs unclean, 16 pgs degraded (PG_DEGRADED)
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When the OSD comes back online, the cluster log records the cluster's return
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to a health state:
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::
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2017-07-25 10:11:11.526841 mon.a mon.0 172.21.9.34:6789/0 109 : cluster [WRN] Health check update: Degraded data redundancy: 2 pgs unclean, 2 pgs degraded, 2 pgs undersized (PG_DEGRADED)
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2017-07-25 10:11:13.535493 mon.a mon.0 172.21.9.34:6789/0 110 : cluster [INF] Health check cleared: PG_DEGRADED (was: Degraded data redundancy: 2 pgs unclean, 2 pgs degraded, 2 pgs undersized)
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2017-07-25 10:11:13.535577 mon.a mon.0 172.21.9.34:6789/0 111 : cluster [INF] Cluster is now healthy
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Detecting configuration issues
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==============================
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In addition to the health checks that Ceph continuously runs on its
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own status, there are some configuration issues that may only be detected
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by an external tool.
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Use the `ceph-medic`_ tool to run these additional checks on your Ceph
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cluster's configuration.
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Checking a Cluster's Usage Stats
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================================
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To check a cluster's data usage and data distribution among pools, you can
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use the ``df`` option. It is similar to Linux ``df``. Execute
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the following::
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ceph df
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The **GLOBAL** section of the output provides an overview of the amount of
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storage your cluster uses for your data.
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- **SIZE:** The overall storage capacity of the cluster.
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- **AVAIL:** The amount of free space available in the cluster.
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- **RAW USED:** The amount of raw storage used.
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- **% RAW USED:** The percentage of raw storage used. Use this number in
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conjunction with the ``full ratio`` and ``near full ratio`` to ensure that
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you are not reaching your cluster's capacity. See `Storage Capacity`_ for
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additional details.
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The **POOLS** section of the output provides a list of pools and the notional
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usage of each pool. The output from this section **DOES NOT** reflect replicas,
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clones or snapshots. For example, if you store an object with 1MB of data, the
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notional usage will be 1MB, but the actual usage may be 2MB or more depending
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on the number of replicas, clones and snapshots.
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- **NAME:** The name of the pool.
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- **ID:** The pool ID.
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- **USED:** The notional amount of data stored in kilobytes, unless the number
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appends **M** for megabytes or **G** for gigabytes.
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- **%USED:** The notional percentage of storage used per pool.
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- **MAX AVAIL:** An estimate of the notional amount of data that can be written
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to this pool.
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- **Objects:** The notional number of objects stored per pool.
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.. note:: The numbers in the **POOLS** section are notional. They are not
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inclusive of the number of replicas, shapshots or clones. As a result,
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the sum of the **USED** and **%USED** amounts will not add up to the
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**RAW USED** and **%RAW USED** amounts in the **GLOBAL** section of the
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output.
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.. note:: The **MAX AVAIL** value is a complicated function of the
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replication or erasure code used, the CRUSH rule that maps storage
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to devices, the utilization of those devices, and the configured
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mon_osd_full_ratio.
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Checking OSD Status
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===================
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You can check OSDs to ensure they are ``up`` and ``in`` by executing::
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ceph osd stat
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Or::
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ceph osd dump
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You can also check view OSDs according to their position in the CRUSH map. ::
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ceph osd tree
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Ceph will print out a CRUSH tree with a host, its OSDs, whether they are up
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and their weight. ::
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# id weight type name up/down reweight
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-1 3 pool default
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-3 3 rack mainrack
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-2 3 host osd-host
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0 1 osd.0 up 1
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1 1 osd.1 up 1
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2 1 osd.2 up 1
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For a detailed discussion, refer to `Monitoring OSDs and Placement Groups`_.
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Checking Monitor Status
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=======================
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If your cluster has multiple monitors (likely), you should check the monitor
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quorum status after you start the cluster before reading and/or writing data. A
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quorum must be present when multiple monitors are running. You should also check
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monitor status periodically to ensure that they are running.
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To see display the monitor map, execute the following::
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ceph mon stat
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Or::
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ceph mon dump
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To check the quorum status for the monitor cluster, execute the following::
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ceph quorum_status
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Ceph will return the quorum status. For example, a Ceph cluster consisting of
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three monitors may return the following:
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.. code-block:: javascript
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{ "election_epoch": 10,
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"quorum": [
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0,
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1,
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2],
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"monmap": { "epoch": 1,
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"fsid": "444b489c-4f16-4b75-83f0-cb8097468898",
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"modified": "2011-12-12 13:28:27.505520",
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"created": "2011-12-12 13:28:27.505520",
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"mons": [
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{ "rank": 0,
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"name": "a",
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"addr": "127.0.0.1:6789\/0"},
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{ "rank": 1,
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"name": "b",
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"addr": "127.0.0.1:6790\/0"},
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{ "rank": 2,
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"name": "c",
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"addr": "127.0.0.1:6791\/0"}
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]
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}
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}
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Checking MDS Status
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===================
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Metadata servers provide metadata services for Ceph FS. Metadata servers have
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two sets of states: ``up | down`` and ``active | inactive``. To ensure your
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metadata servers are ``up`` and ``active``, execute the following::
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ceph mds stat
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To display details of the metadata cluster, execute the following::
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ceph fs dump
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Checking Placement Group States
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===============================
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Placement groups map objects to OSDs. When you monitor your
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placement groups, you will want them to be ``active`` and ``clean``.
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For a detailed discussion, refer to `Monitoring OSDs and Placement Groups`_.
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.. _Monitoring OSDs and Placement Groups: ../monitoring-osd-pg
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Using the Admin Socket
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======================
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The Ceph admin socket allows you to query a daemon via a socket interface.
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By default, Ceph sockets reside under ``/var/run/ceph``. To access a daemon
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via the admin socket, login to the host running the daemon and use the
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following command::
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ceph daemon {daemon-name}
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ceph daemon {path-to-socket-file}
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For example, the following are equivalent::
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ceph daemon osd.0 foo
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ceph daemon /var/run/ceph/ceph-osd.0.asok foo
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To view the available admin socket commands, execute the following command::
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ceph daemon {daemon-name} help
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The admin socket command enables you to show and set your configuration at
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runtime. See `Viewing a Configuration at Runtime`_ for details.
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Additionally, you can set configuration values at runtime directly (i.e., the
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admin socket bypasses the monitor, unlike ``ceph tell {daemon-type}.{id}
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injectargs``, which relies on the monitor but doesn't require you to login
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directly to the host in question ).
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.. _Viewing a Configuration at Runtime: ../../configuration/ceph-conf#ceph-runtime-config
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.. _Storage Capacity: ../../configuration/mon-config-ref#storage-capacity
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.. _ceph-medic: http://docs.ceph.com/ceph-medic/master/
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