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10 KiB
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.. _cephfs-health-messages:
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======================
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CephFS health messages
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======================
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Cluster health checks
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=====================
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The Ceph monitor daemons will generate health messages in response
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to certain states of the file system map structure (and the enclosed MDS maps).
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Message: mds rank(s) *ranks* have failed
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Description: One or more MDS ranks are not currently assigned to
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an MDS daemon; the cluster will not recover until a suitable replacement
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daemon starts.
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Message: mds rank(s) *ranks* are damaged
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Description: One or more MDS ranks has encountered severe damage to
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its stored metadata, and cannot start again until it is repaired.
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Message: mds cluster is degraded
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Description: One or more MDS ranks are not currently up and running, clients
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may pause metadata IO until this situation is resolved. This includes
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ranks being failed or damaged, and additionally includes ranks
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which are running on an MDS but have not yet made it to the *active*
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state (e.g. ranks currently in *replay* state).
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Message: mds *names* are laggy
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Description: The named MDS daemons have failed to send beacon messages
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to the monitor for at least ``mds_beacon_grace`` (default 15s), while
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they are supposed to send beacon messages every ``mds_beacon_interval``
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(default 4s). The daemons may have crashed. The Ceph monitor will
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automatically replace laggy daemons with standbys if any are available.
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Message: insufficient standby daemons available
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Description: One or more file systems are configured to have a certain number
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of standby daemons available (including daemons in standby-replay) but the
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cluster does not have enough standby daemons. The standby daemons not in replay
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count towards any file system (i.e. they may overlap). This warning can
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configured by setting ``ceph fs set <fs> standby_count_wanted <count>``. Use
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zero for ``count`` to disable.
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Daemon-reported health checks
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=============================
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MDS daemons can identify a variety of unwanted conditions, and
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indicate these to the operator in the output of ``ceph status``.
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These conditions have human readable messages, and additionally
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a unique code starting with ``MDS_``.
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.. highlight:: console
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``ceph health detail`` shows the details of the conditions. Following
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is a typical health report from a cluster experiencing MDS related
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performance issues::
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$ ceph health detail
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HEALTH_WARN 1 MDSs report slow metadata IOs; 1 MDSs report slow requests
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MDS_SLOW_METADATA_IO 1 MDSs report slow metadata IOs
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mds.fs-01(mds.0): 3 slow metadata IOs are blocked > 30 secs, oldest blocked for 51123 secs
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MDS_SLOW_REQUEST 1 MDSs report slow requests
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mds.fs-01(mds.0): 5 slow requests are blocked > 30 secs
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Where, for instance, ``MDS_SLOW_REQUEST`` is the unique code representing the
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condition where requests are taking long time to complete. And the following
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description shows its severity and the MDS daemons which are serving these
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slow requests.
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This page lists the health checks raised by MDS daemons. For the checks from
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other daemons, please see :ref:`health-checks`.
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``MDS_TRIM``
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------------
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Message
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"Behind on trimming..."
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Description
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CephFS maintains a metadata journal that is divided into
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*log segments*. The length of journal (in number of segments) is controlled
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by the setting ``mds_log_max_segments``, and when the number of segments
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exceeds that setting the MDS starts writing back metadata so that it
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can remove (trim) the oldest segments. If this writeback is happening
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too slowly, or a software bug is preventing trimming, then this health
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message may appear. The threshold for this message to appear is controlled by
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the config option ``mds_log_warn_factor``, the default is 2.0.
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``MDS_HEALTH_CLIENT_LATE_RELEASE``, ``MDS_HEALTH_CLIENT_LATE_RELEASE_MANY``
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---------------------------------------------------------------------------
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Message
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"Client *name* failing to respond to capability release"
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Description
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CephFS clients are issued *capabilities* by the MDS, which
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are like locks. Sometimes, for example when another client needs access,
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the MDS will request clients release their capabilities. If the client
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is unresponsive or buggy, it might fail to do so promptly or fail to do
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so at all. This message appears if a client has taken longer than
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``session_timeout`` (default 60s) to comply.
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``MDS_CLIENT_RECALL``, ``MDS_HEALTH_CLIENT_RECALL_MANY``
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--------------------------------------------------------
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Message
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"Client *name* failing to respond to cache pressure"
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Description
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Clients maintain a metadata cache. Items (such as inodes) in the
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client cache are also pinned in the MDS cache, so when the MDS needs to shrink
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its cache (to stay within ``mds_cache_memory_limit``), it sends messages to
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clients to shrink their caches too. If the client is unresponsive or buggy,
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this can prevent the MDS from properly staying within its cache limits and it
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may eventually run out of memory and crash. This message appears if a client
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has failed to release more than
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``mds_recall_warning_threshold`` capabilities (decaying with a half-life of
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``mds_recall_max_decay_rate``) within the last
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``mds_recall_warning_decay_rate`` second.
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``MDS_CLIENT_OLDEST_TID``, ``MDS_CLIENT_OLDEST_TID_MANY``
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---------------------------------------------------------
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Message
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"Client *name* failing to advance its oldest client/flush tid"
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Description
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The CephFS client-MDS protocol uses a field called the
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*oldest tid* to inform the MDS of which client requests are fully
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complete and may therefore be forgotten about by the MDS. If a buggy
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client is failing to advance this field, then the MDS may be prevented
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from properly cleaning up resources used by client requests. This message
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appears if a client appears to have more than ``max_completed_requests``
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(default 100000) requests that are complete on the MDS side but haven't
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yet been accounted for in the client's *oldest tid* value. The last tid
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used by the MDS to trim completed client requests (or flush) is included
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as part of `session ls` (or `client ls`) command as a debug aid.
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``MDS_DAMAGE``
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--------------
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Message
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"Metadata damage detected"
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Description
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Corrupt or missing metadata was encountered when reading
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from the metadata pool. This message indicates that the damage was
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sufficiently isolated for the MDS to continue operating, although
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client accesses to the damaged subtree will return IO errors. Use
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the ``damage ls`` admin socket command to get more detail on the damage.
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This message appears as soon as any damage is encountered.
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``MDS_HEALTH_READ_ONLY``
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------------------------
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Message
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"MDS in read-only mode"
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Description
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The MDS has gone into readonly mode and will return EROFS
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error codes to client operations that attempt to modify any metadata. The
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MDS will go into readonly mode if it encounters a write error while
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writing to the metadata pool, or if forced to by an administrator using
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the *force_readonly* admin socket command.
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``MDS_SLOW_REQUEST``
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--------------------
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Message
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"*N* slow requests are blocked"
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Description
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One or more client requests have not been completed promptly,
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indicating that the MDS is either running very slowly, or that the RADOS
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cluster is not acknowledging journal writes promptly, or that there is a bug.
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Use the ``ops`` admin socket command to list outstanding metadata operations.
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This message appears if any client requests have taken longer than
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``mds_op_complaint_time`` (default 30s).
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``MDS_CACHE_OVERSIZED``
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-----------------------
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Message
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"Too many inodes in cache"
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Description
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The MDS is not succeeding in trimming its cache to comply with the
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limit set by the administrator. If the MDS cache becomes too large, the daemon
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may exhaust available memory and crash. By default, this message appears if
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the actual cache size (in memory) is at least 50% greater than
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``mds_cache_memory_limit`` (default 4GB). Modify ``mds_health_cache_threshold``
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to set the warning ratio.
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``FS_WITH_FAILED_MDS``
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----------------------
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Message
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"Some MDS ranks do not have standby replacements"
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Description
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Normally, a failed MDS rank will be replaced by a standby MDS. This situation
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is transient and is not considered critical. However, if there are no standby
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MDSs available to replace an active MDS rank, this health warning is generated.
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``MDS_INSUFFICIENT_STANDBY``
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----------------------------
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Message
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"Insufficient number of available standby(-replay) MDS daemons than configured"
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Description
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The minimum number of standby(-replay) MDS daemons can be configured by setting
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``standby_count_wanted`` configuration variable. This health warning is generated
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when the configured value mismatches the number of standby(-replay) MDS daemons
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available.
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``FS_DEGRADED``
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----------------------------
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Message
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"Some MDS ranks have been marked failed or damaged"
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Description
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When one or more MDS rank ends up in failed or damaged state due to
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an unrecoverable error. The file system may be partially or fully
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unavailable when one (or more) ranks are offline.
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``MDS_UP_LESS_THAN_MAX``
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----------------------------
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Message
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"Number of active ranks are less than configured number of maximum MDSs"
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Description
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The maximum number of MDS ranks can be configured by setting ``max_mds``
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configuration variable. This health warning is generated when the number
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of MDS ranks falls below this configured value.
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``MDS_ALL_DOWN``
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----------------------------
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Message
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"None of the MDS ranks are available (file system offline)"
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Description
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All MDS ranks are unavailable resulting in the file system to be completely
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offline.
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``MDS_CLIENTS_LAGGY``
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----------------------------
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Message
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"Client *ID* is laggy; not evicted because some OSD(s) is/are laggy"
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Description
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If OSD(s) is laggy (due to certain conditions like network cut-off, etc)
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then it might make clients laggy(session might get idle or cannot flush
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dirty data for cap revokes). If ``defer_client_eviction_on_laggy_osds`` is
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set to true (default true), client eviction will not take place and thus
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this health warning will be generated.
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