
=============
Health checks
=============

Overview
========

There is a finite set of possible health messages that a Ceph cluster can
raise -- these are defined as *health checks* which have unique identifiers.

The identifier is a terse pseudo-human-readable (i.e. like a variable name)
string.  It is intended to enable tools (such as UIs) to make sense of
health checks, and present them in a way that reflects their meaning.

This page lists the health checks that are raised by the monitor and manager
daemons.  In addition to these, you may also see health checks that originate
from MDS daemons (see :doc:`/cephfs/health-messages`), and health checks
that are defined by ceph-mgr python modules.

Definitions
===========


OSDs
----

OSD_DOWN
________

One or more OSDs are marked down.  The ceph-osd daemon may have been
stopped, or peer OSDs may be unable to reach the OSD over the network.
Common causes include a stopped or crashed daemon, a down host, or a
network outage.

Verify the host is healthy, the daemon is started, and network is
functioning.  If the daemon has crashed, the daemon log file
(``/var/log/ceph/ceph-osd.*``) may contain debugging information.

OSD_<crush type>_DOWN
_____________________

(e.g. OSD_HOST_DOWN, OSD_ROOT_DOWN)

All the OSDs within a particular CRUSH subtree are marked down, for example
all OSDs on a host.

OSD_ORPHAN
__________

An OSD is referenced in the CRUSH map hierarchy but does not exist.

The OSD can be removed from the CRUSH hierarchy with::

  ceph osd crush rm osd.<id>

OSD_OUT_OF_ORDER_FULL
_____________________

The utilization thresholds for `backfillfull`, `nearfull`, `full`,
and/or `failsafe_full` are not ascending.  In particular, we expect
`backfillfull < nearfull`, `nearfull < full`, and `full <
failsafe_full`.

The thresholds can be adjusted with::

  ceph osd set-backfillfull-ratio <ratio>
  ceph osd set-nearfull-ratio <ratio>
  ceph osd set-full-ratio <ratio>


OSD_FULL
________

One or more OSDs has exceeded the `full` threshold and is preventing
the cluster from servicing writes.

Utilization by pool can be checked with::

  ceph df

The currently defined `full` ratio can be seen with::

  ceph osd dump | grep full_ratio

A short-term workaround to restore write availability is to raise the full
threshold by a small amount::

  ceph osd set-full-ratio <ratio>

New storage should be added to the cluster by deploying more OSDs or
existing data should be deleted in order to free up space.
  
OSD_BACKFILLFULL
________________

One or more OSDs has exceeded the `backfillfull` threshold, which will
prevent data from being allowed to rebalance to this device.  This is
an early warning that rebalancing may not be able to complete and that
the cluster is approaching full.

Utilization by pool can be checked with::

  ceph df

OSD_NEARFULL
____________

One or more OSDs has exceeded the `nearfull` threshold.  This is an early
warning that the cluster is approaching full.

Utilization by pool can be checked with::

  ceph df

OSDMAP_FLAGS
____________

One or more cluster flags of interest has been set.  These flags include:

* *full* - the cluster is flagged as full and cannot service writes
* *pauserd*, *pausewr* - paused reads or writes
* *noup* - OSDs are not allowed to start
* *nodown* - OSD failure reports are being ignored, such that the
  monitors will not mark OSDs `down`
* *noin* - OSDs that were previously marked `out` will not be marked
  back `in` when they start
* *noout* - down OSDs will not automatically be marked out after the
  configured interval
* *nobackfill*, *norecover*, *norebalance* - recovery or data
  rebalancing is suspended
* *noscrub*, *nodeep_scrub* - scrubbing is disabled
* *notieragent* - cache tiering activity is suspended

With the exception of *full*, these flags can be set or cleared with::

  ceph osd set <flag>
  ceph osd unset <flag>
    
OSD_FLAGS
_________

One or more OSDs has a per-OSD flag of interest set.  These flags include:

* *noup*: OSD is not allowed to start
* *nodown*: failure reports for this OSD will be ignored
* *noin*: if this OSD was previously marked `out` automatically
  after a failure, it will not be marked in when it stats
* *noout*: if this OSD is down it will not automatically be marked
  `out` after the configured interval

Per-OSD flags can be set and cleared with::

  ceph osd add-<flag> <osd-id>
  ceph osd rm-<flag> <osd-id>

For example, ::

  ceph osd rm-nodown osd.123

OLD_CRUSH_TUNABLES
__________________

The CRUSH map is using very old settings and should be updated.  The
oldest tunables that can be used (i.e., the oldest client version that
can connect to the cluster) without triggering this health warning is
determined by the ``mon_crush_min_required_version`` config option.
See :doc:`/rados/operations/crush-map/#tunables` for more information.

OLD_CRUSH_STRAW_CALC_VERSION
____________________________

The CRUSH map is using an older, non-optimal method for calculating
intermediate weight values for ``straw`` buckets.

The CRUSH map should be updated to use the newer method
(``straw_calc_version=1``).  See
:doc:`/rados/operations/crush-map/#tunables` for more information.

CACHE_POOL_NO_HIT_SET
_____________________

One or more cache pools is not configured with a *hit set* to track
utilization, which will prevent the tiering agent from identifying
cold objects to flush and evict from the cache.

Hit sets can be configured on the cache pool with::

  ceph osd pool set <poolname> hit_set_type <type>
  ceph osd pool set <poolname> hit_set_period <period-in-seconds>
  ceph osd pool set <poolname> hit_set_count <number-of-hitsets>
  ceph osd pool set <poolname> hit_set_fpp <target-false-positive-rate>  

OSD_NO_SORTBITWISE
__________________

No pre-luminous v12.y.z OSDs are running but the ``sortbitwise`` flag has not
been set.

The ``sortbitwise`` flag must be set before luminous v12.y.z or newer
OSDs can start.  You can safely set the flag with::

  ceph osd set sortbitwise

POOL_FULL
_________

One or more pools has reached its quota and is no longer allowing writes.

Pool quotas and utilization can be seen with::

  ceph df detail

You can either raise the pool quota with::

  ceph osd pool set-quota <poolname> max_objects <num-objects>
  ceph osd pool set-quota <poolname> max_bytes <num-bytes>

or delete some existing data to reduce utilization.


Data health (pools & placement groups)
--------------------------------------

PG_AVAILABILITY
_______________

Data availability is reduced, meaning that the cluster is unable to
service potential read or write requests for some data in the cluster.
Specifically, one or more PGs is in a state that does not allow IO
requests to be serviced.  Problematic PG states include *peering*,
*stale*, *incomplete*, and the lack of *active* (if those conditions do not clear
quickly).

Detailed information about which PGs are affected is available from::

  ceph health detail

In most cases the root cause is that one or more OSDs is currently
down; see the dicussion for ``OSD_DOWN`` above.

The state of specific problematic PGs can be queried with::

  ceph tell <pgid> query

PG_DEGRADED
___________

Data redundancy is reduced for some data, meaning the cluster does not
have the desired number of replicas for all data (for replicated
pools) or erasure code fragments (for erasure coded pools).
Specifically, one or more PGs:

* has the *degraded* or *undersized* flag set, meaning there are not
  enough instances of that placement group in the cluster;
* has not had the *clean* flag set for some time.

Detailed information about which PGs are affected is available from::

  ceph health detail

In most cases the root cause is that one or more OSDs is currently
down; see the dicussion for ``OSD_DOWN`` above.

The state of specific problematic PGs can be queried with::

  ceph tell <pgid> query


PG_DEGRADED_FULL
________________

Data redundancy may be reduced or at risk for some data due to a lack
of free space in the cluster.  Specifically, one or more PGs has the
*backfill_toofull* or *recovery_toofull* flag set, meaning that the
cluster is unable to migrate or recover data because one or more OSDs
is above the *backfillfull* threshold.

See the discussion for *OSD_BACKFILLFULL* or *OSD_FULL* above for
steps to resolve this condition.

PG_DAMAGED
__________

Data scrubbing has discovered some problems with data consistency in
the cluster.  Specifically, one or more PGs has the *inconsistent* or
*snaptrim_error* flag is set, indicating an earlier scrub operation
found a problem, or that the *repair* flag is set, meaning a repair
for such an inconsistency is currently in progress.

See :doc:`pg-repair` for more information.

OSD_SCRUB_ERRORS
________________

Recent OSD scrubs have uncovered inconsistencies. This error is generally
paired with *PG_DAMANGED* (see above).

See :doc:`pg-repair` for more information.

CACHE_POOL_NEAR_FULL
____________________

A cache tier pool is nearly full.  Full in this context is determined
by the ``target_max_bytes`` and ``target_max_objects`` properties on
the cache pool.  Once the pool reaches the target threshold, write
requests to the pool may block while data is flushed and evicted
from the cache, a state that normally leads to very high latencies and
poor performance.

The cache pool target size can be adjusted with::

  ceph osd pool set <cache-pool-name> target_max_bytes <bytes>
  ceph osd pool set <cache-pool-name> target_max_objects <objects>

Normal cache flush and evict activity may also be throttled due to reduced
availability or performance of the base tier, or overall cluster load.

TOO_FEW_PGS
___________

The number of PGs in use in the cluster is below the configurable
threshold of ``mon_pg_warn_min_per_osd`` PGs per OSD.  This can lead
to suboptimizal distribution and balance of data across the OSDs in
the cluster, and similar reduce overall performance.

This may be an expected condition if data pools have not yet been
created.

The PG count for existing pools can be increased or new pools can be
created.  Please refer to
:doc:`placement-groups#Choosing-the-number-of-Placement-Groups` for
more information.

TOO_MANY_PGS
____________

The number of PGs in use in the cluster is above the configurable
threshold of ``mon_max_pg_per_osd`` PGs per OSD.  If this threshold is
exceed the cluster will not allow new pools to be created, pool `pg_num` to
be increased, or pool replication to be increased (any of which would lead to
more PGs in the cluster).  A large number of PGs can lead
to higher memory utilization for OSD daemons, slower peering after
cluster state changes (like OSD restarts, additions, or removals), and
higher load on the Manager and Monitor daemons.

The simplest way to mitigate the problem is to increase the number of
OSDs in the cluster by adding more hardware.  Note that the OSD count
used for the purposes of this health check is the number of "in" OSDs,
so marking "out" OSDs "in" (if there are any) can also help::

  ceph osd in <osd id(s)>

Please refer to
:doc:`placement-groups#Choosing-the-number-of-Placement-Groups` for
more information.

SMALLER_PGP_NUM
_______________

One or more pools has a ``pgp_num`` value less than ``pg_num``.  This
is normally an indication that the PG count was increased without
also increasing the placement behavior.

This is sometimes done deliberately to separate out the `split` step
when the PG count is adjusted from the data migration that is needed
when ``pgp_num`` is changed.

This is normally resolved by setting ``pgp_num`` to match ``pg_num``,
triggering the data migration, with::

  ceph osd pool set <pool> pgp_num <pg-num-value>

MANY_OBJECTS_PER_PG
___________________

One or more pools has an average number of objects per PG that is
significantly higher than the overall cluster average.  The specific
threshold is controlled by the ``mon_pg_warn_max_object_skew``
configuration value.

This is usually an indication that the pool(s) containing most of the
data in the cluster have too few PGs, and/or that other pools that do
not contain as much data have too many PGs.  See the discussion of
*TOO_MANY_PGS* above.

The threshold can be raised to silence the health warning by adjusting
the ``mon_pg_warn_max_object_skew`` config option on the monitors.

POOL_APP_NOT_ENABLED
____________________

A pool exists that contains one or more objects but has not been
tagged for use by a particular application.

Resolve this warning by labeling the pool for use by an application.  For
example, if the pool is used by RBD,::

  rbd pool init <poolname>

If the pool is being used by a custom application 'foo', you can also label
via the low-level command::

  ceph osd pool application enable foo

For more information, see :doc:`pools.rst#associate-pool-to-application`.

POOL_FULL
_________

One or more pools has reached (or is very close to reaching) its
quota.  The threshold to trigger this error condition is controlled by
the ``mon_pool_quota_crit_threshold`` configuration option.

Pool quotas can be adjusted up or down (or removed) with::

  ceph osd pool set-quota <pool> max_bytes <bytes>
  ceph osd pool set-quota <pool> max_objects <objects>

Setting the quota value to 0 will disable the quota.  

POOL_NEAR_FULL
______________

One or more pools is approaching is quota.  The threshold to trigger
this warning condition is controlled by the
``mon_pool_quota_warn_threshold`` configuration option.

Pool quotas can be adjusted up or down (or removed) with::

  ceph osd pool set-quota <pool> max_bytes <bytes>
  ceph osd pool set-quota <pool> max_objects <objects>

Setting the quota value to 0 will disable the quota.

OBJECT_MISPLACED
________________

One or more objects in the cluster is not stored on the node the
cluster would like it to be stored on.  This is an indication that
data migration due to some recent cluster change has not yet completed.

Misplaced data is not a dangerous condition in and of itself; data
consistency is never at risk, and old copies of objects are never
removed until the desired number of new copies (in the desired
locations) are present.

OBJECT_UNFOUND
______________

One or more objects in the cluster cannot be found.  Specifically, the
OSDs know that a new or updated copy of an object should exist, but a
copy of that version of the object has not been found on OSDs that are
currently online.

Read or write requests to unfound objects will block.

Ideally, a down OSD can be brought back online that has the more
recent copy of the unfound object.  Candidate OSDs can be identified from the
peering state for the PG(s) responsible for the unfound object::

  ceph tell <pgid> query

If the latest copy of the object is not available, the cluster can be
told to roll back to a previous version of the object.  See
:doc:`troubleshooting-pg#Unfound-objects` for more information.

REQUEST_SLOW
____________

One or more OSD requests is taking a long time to process.  This can
be an indication of extreme load, a slow storage device, or a software
bug.

The request queue on the OSD(s) in question can be queried with the
following command, executed from the OSD host::

  ceph daemon osd.<id> ops

A summary of the slowest recent requests can be seen with::

  ceph daemon osd.<id> dump_historic_ops

The location of an OSD can be found with::

  ceph osd find osd.<id>

REQUEST_STUCK
_____________

One or more OSD requests has been blocked for an extremely long time.
This is an indication that either the cluster has been unhealthy for
an extended period of time (e.g., not enough running OSDs) or there is
some internal problem with the OSD.  See the dicussion of
*REQUEST_SLOW* above.

PG_NOT_SCRUBBED
_______________

One or more PGs has not been scrubbed recently.  PGs are normally
scrubbed every ``mon_scrub_interval`` seconds, and this warning
triggers when ``mon_warn_not_scrubbed`` such intervals have elapsed
without a scrub.

PGs will not scrub if they are not flagged as *clean*, which may
happen if they are misplaced or degraded (see *PG_AVAILABILITY* and
*PG_DEGRADED* above).

You can manually initiate a scrub of a clean PG with::

  ceph pg scrub <pgid>

PG_NOT_DEEP_SCRUBBED
____________________

One or more PGs has not been deep scrubbed recently.  PGs are normally
scrubbed every ``osd_deep_mon_scrub_interval`` seconds, and this warning
triggers when ``mon_warn_not_deep_scrubbed`` such intervals have elapsed
without a scrub.

PGs will not (deep) scrub if they are not flagged as *clean*, which may
happen if they are misplaced or degraded (see *PG_AVAILABILITY* and
*PG_DEGRADED* above).

You can manually initiate a scrub of a clean PG with::

  ceph pg deep-scrub <pgid>
