.. _rados_pools:

=======
 Pools
=======
Pools are logical partitions that are used to store objects.

Pools provide:

- **Resilience**: It is possible to set the number of OSDs that are allowed to
  fail without any data being lost. If your cluster uses replicated pools, the
  number of OSDs that can fail without data loss is the number of replicas.
  For example: a typical configuration stores an object and two additional
  copies (that is: ``size = 3``), but you can configure the number of replicas
  on a per-pool basis. For `erasure coded pools <../erasure-code>`_, resilience
  is defined as the number of coding chunks (for example, ``m = 2`` in the
  **erasure code profile**).

- **Placement Groups**: You can set the number of placement groups for the
  pool. A typical configuration targets approximately 100 placement groups per
  OSD, providing optimal balancing without consuming many computing resources.
  When setting up multiple pools, be careful to set a reasonable number of
  placement groups for each pool and for the cluster as a whole. Note that each
  PG belongs to a specific pool: when multiple pools use the same OSDs, make
  sure that the **sum** of PG replicas per OSD is in the desired PG per OSD
  target range. Use the `pgcalc`_ tool to calculate the number of placement
  groups to set for your pool.

- **CRUSH Rules**: When data is stored in a pool, the placement of the object
  and its replicas (or chunks, in the case of erasure-coded pools) in your
  cluster is governed by CRUSH rules. Custom CRUSH rules can be created for a
  pool if the default rule does not fit your use case.

- **Snapshots**: The command ``ceph osd pool mksnap`` creates a snapshot of a
  pool. 

Pool Names
==========

Pool names beginning with ``.`` are reserved for use by Ceph's internal
operations. Please do not create or manipulate pools with these names.

List Pools
==========

To list your cluster's pools, execute:

.. prompt:: bash $

   ceph osd lspools

.. _createpool:

Create a Pool
=============

Before creating pools, refer to the `Pool, PG and CRUSH Config Reference`_.
Ideally, you should override the default value for the number of placement
groups in your Ceph configuration file, as the default is NOT ideal.
For details on placement group numbers refer to `setting the number of placement groups`_

.. note:: Starting with Luminous, all pools need to be associated to the
   application using the pool. See `Associate Pool to Application`_ below for
   more information.

For example:

.. prompt:: bash $

	osd pool default pg num = 100
	osd pool default pgp num = 100

To create a pool, execute:

.. prompt:: bash $

	ceph osd pool create {pool-name} [{pg-num} [{pgp-num}]] [replicated] \
             [crush-rule-name] [expected-num-objects]
	ceph osd pool create {pool-name} [{pg-num} [{pgp-num}]]   erasure \
             [erasure-code-profile] [crush-rule-name] [expected_num_objects] [--autoscale-mode=<on,off,warn>]

Where:

``{pool-name}``

:Description: The name of the pool. It must be unique.
:Type: String
:Required: Yes.

``{pg-num}``

:Description: The total number of placement groups for the pool. See `Placement
              Groups`_  for details on calculating a suitable number. The
              default value ``8`` is NOT suitable for most systems.

:Type: Integer
:Required: Yes.
:Default: 8

``{pgp-num}``

:Description: The total number of placement groups for placement purposes. This
              **should be equal to the total number of placement groups**, except
              for placement group splitting scenarios.

:Type: Integer
:Required: Yes. Picks up default or Ceph configuration value if not specified.
:Default: 8

``{replicated|erasure}``

:Description: The pool type which may either be **replicated** to
              recover from lost OSDs by keeping multiple copies of the
              objects or **erasure** to get a kind of
              `generalized RAID5 <../erasure-code>`_ capability.
              The **replicated** pools require more
              raw storage but implement all Ceph operations. The
              **erasure** pools require less raw storage but only
              implement a subset of the available operations.

:Type: String
:Required: No.
:Default: replicated

``[crush-rule-name]``

:Description: The name of a CRUSH rule to use for this pool.  The specified
              rule must exist.

:Type: String
:Required: No.
:Default: For **replicated** pools it is the rule specified by the ``osd
          pool default crush rule`` config variable.  This rule must exist.
          For **erasure** pools it is ``erasure-code`` if the ``default``
          `erasure code profile`_ is used or ``{pool-name}`` otherwise.  This
          rule will be created implicitly if it doesn't exist already.


``[erasure-code-profile=profile]``

.. _erasure code profile: ../erasure-code-profile

:Description: For **erasure** pools only. Use the `erasure code profile`_. It
              must be an existing profile as defined by
              **osd erasure-code-profile set**.

:Type: String
:Required: No.

``--autoscale-mode=<on,off,warn>``

:Description: Autoscale mode

:Type: String
:Required: No.
:Default:  The default behavior is controlled by the ``osd pool default pg autoscale mode`` option.

If you set the autoscale mode to ``on`` or ``warn``, you can let the system autotune or recommend changes to the number of placement groups in your pool based on actual usage.  If you leave it off, then you should refer to `Placement Groups`_ for more information.

.. _Placement Groups: ../placement-groups

``[expected-num-objects]``

:Description: The expected number of objects for this pool. By setting this value (
              together with a negative **filestore merge threshold**), the PG folder
              splitting would happen at the pool creation time, to avoid the latency
              impact to do a runtime folder splitting.

:Type: Integer
:Required: No.
:Default: 0, no splitting at the pool creation time.

.. _associate-pool-to-application:

Associate Pool to Application
=============================

Pools need to be associated with an application before use. Pools that will be
used with CephFS or pools that are automatically created by RGW are
automatically associated. Pools that are intended for use with RBD should be
initialized using the ``rbd`` tool (see `Block Device Commands`_ for more
information).

For other cases, you can manually associate a free-form application name to
a pool.:

.. prompt:: bash $

   ceph osd pool application enable {pool-name} {application-name}

.. note:: CephFS uses the application name ``cephfs``, RBD uses the
   application name ``rbd``, and RGW uses the application name ``rgw``.

Set Pool Quotas
===============

You can set pool quotas for the maximum number of bytes and/or the maximum
number of objects per pool:

.. prompt:: bash $

   ceph osd pool set-quota {pool-name} [max_objects {obj-count}] [max_bytes {bytes}]

For example:

.. prompt:: bash $

   ceph osd pool set-quota data max_objects 10000

To remove a quota, set its value to ``0``.


Delete a Pool
=============

To delete a pool, execute:

.. prompt:: bash $

   ceph osd pool delete {pool-name} [{pool-name} --yes-i-really-really-mean-it]


To remove a pool the mon_allow_pool_delete flag must be set to true in the Monitor's
configuration. Otherwise they will refuse to remove a pool.

See `Monitor Configuration`_ for more information.

.. _Monitor Configuration: ../../configuration/mon-config-ref

If you created your own rules for a pool you created, you should consider
removing them when you no longer need your pool:

.. prompt:: bash $

   ceph osd pool get {pool-name} crush_rule

If the rule was "123", for example, you can check the other pools like so:

.. prompt:: bash $

	ceph osd dump | grep "^pool" | grep "crush_rule 123"

If no other pools use that custom rule, then it's safe to delete that
rule from the cluster.

If you created users with permissions strictly for a pool that no longer
exists, you should consider deleting those users too:


.. prompt:: bash $

	ceph auth ls | grep -C 5 {pool-name}
	ceph auth del {user}


Rename a Pool
=============

To rename a pool, execute:

.. prompt:: bash $

   ceph osd pool rename {current-pool-name} {new-pool-name}

If you rename a pool and you have per-pool capabilities for an authenticated
user, you must update the user's capabilities (i.e., caps) with the new pool
name.

Show Pool Statistics
====================

To show a pool's utilization statistics, execute:

.. prompt:: bash $

   rados df

Additionally, to obtain I/O information for a specific pool or all, execute:

.. prompt:: bash $

   ceph osd pool stats [{pool-name}]


Make a Snapshot of a Pool
=========================

To make a snapshot of a pool, execute:

.. prompt:: bash $

   ceph osd pool mksnap {pool-name} {snap-name}

Remove a Snapshot of a Pool
===========================

To remove a snapshot of a pool, execute:

.. prompt:: bash $

   ceph osd pool rmsnap {pool-name} {snap-name}

.. _setpoolvalues:


Set Pool Values
===============

To set a value to a pool, execute the following:

.. prompt:: bash $

   ceph osd pool set {pool-name} {key} {value}

You may set values for the following keys:

.. _compression_algorithm:

``compression_algorithm``

:Description: Sets inline compression algorithm to use for underlying BlueStore. This setting overrides the `global setting <https://docs.ceph.com/en/latest/rados/configuration/bluestore-config-ref/#inline-compression>`__ of ``bluestore compression algorithm``.

:Type: String
:Valid Settings: ``lz4``, ``snappy``, ``zlib``, ``zstd``

``compression_mode``

:Description: Sets the policy for the inline compression algorithm for underlying BlueStore. This setting overrides the `global setting <http://docs.ceph.com/en/latest/rados/configuration/bluestore-config-ref/#inline-compression>`__ of ``bluestore compression mode``.

:Type: String
:Valid Settings: ``none``, ``passive``, ``aggressive``, ``force``

``compression_min_blob_size``

:Description: Chunks smaller than this are never compressed. This setting overrides the `global setting <http://docs.ceph.com/en/latest/rados/configuration/bluestore-config-ref/#inline-compression>`__ of ``bluestore compression min blob *``.

:Type: Unsigned Integer

``compression_max_blob_size``

:Description: Chunks larger than this are broken into smaller blobs sizing
              ``compression_max_blob_size`` before being compressed.

:Type: Unsigned Integer

.. _size:

``size``

:Description: Sets the number of replicas for objects in the pool.
              See `Set the Number of Object Replicas`_ for further details.
              Replicated pools only.

:Type: Integer

.. _min_size:

``min_size``

:Description: Sets the minimum number of replicas required for I/O.
              See `Set the Number of Object Replicas`_ for further details.
              In the case of Erasure Coded pools this should be set to a value
              greater than 'k' since if we allow IO at the value 'k' there is no
              redundancy and data will be lost in the event of a permanent OSD
              failure. For more information see `Erasure Code
              <../erasure-code>`_

:Type: Integer
:Version: ``0.54`` and above

.. _pg_num:

``pg_num``

:Description: The effective number of placement groups to use when calculating
              data placement.
:Type: Integer
:Valid Range: Superior to ``pg_num`` current value.

.. _pgp_num:

``pgp_num``

:Description: The effective number of placement groups for placement to use
              when calculating data placement.

:Type: Integer
:Valid Range: Equal to or less than ``pg_num``.

.. _crush_rule:

``crush_rule``

:Description: The rule to use for mapping object placement in the cluster.
:Type: String

.. _allow_ec_overwrites:

``allow_ec_overwrites``

:Description: Whether writes to an erasure coded pool can update part
              of an object, so cephfs and rbd can use it. See
              `Erasure Coding with Overwrites`_ for more details.
:Type: Boolean
:Version: ``12.2.0`` and above

.. _hashpspool:

``hashpspool``

:Description: Set/Unset HASHPSPOOL flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag

.. _nodelete:

``nodelete``

:Description: Set/Unset NODELETE flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag
:Version: Version ``FIXME``

.. _nopgchange:

``nopgchange``

:Description: Set/Unset NOPGCHANGE flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag
:Version: Version ``FIXME``

.. _nosizechange:

``nosizechange``

:Description: Set/Unset NOSIZECHANGE flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag
:Version: Version ``FIXME``

.. _bulk:

.. describe:: bulk

   Set/Unset bulk flag on a given pool.

   :Type: Boolean
   :Valid Range: true/1 sets flag, false/0 unsets flag

.. _write_fadvise_dontneed:

``write_fadvise_dontneed``

:Description: Set/Unset WRITE_FADVISE_DONTNEED flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag

.. _noscrub:

``noscrub``

:Description: Set/Unset NOSCRUB flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag

.. _nodeep-scrub:

``nodeep-scrub``

:Description: Set/Unset NODEEP_SCRUB flag on a given pool.
:Type: Integer
:Valid Range: 1 sets flag, 0 unsets flag

.. _hit_set_type:

``hit_set_type``

:Description: Enables hit set tracking for cache pools.
              See `Bloom Filter`_ for additional information.

:Type: String
:Valid Settings: ``bloom``, ``explicit_hash``, ``explicit_object``
:Default: ``bloom``. Other values are for testing.

.. _hit_set_count:

``hit_set_count``

:Description: The number of hit sets to store for cache pools. The higher
              the number, the more RAM consumed by the ``ceph-osd`` daemon.

:Type: Integer
:Valid Range: ``1``. Agent doesn't handle > 1 yet.

.. _hit_set_period:

``hit_set_period``

:Description: The duration of a hit set period in seconds for cache pools.
              The higher the number, the more RAM consumed by the
              ``ceph-osd`` daemon.

:Type: Integer
:Example: ``3600`` 1hr

.. _hit_set_fpp:

``hit_set_fpp``

:Description: The false positive probability for the ``bloom`` hit set type.
              See `Bloom Filter`_ for additional information.

:Type: Double
:Valid Range: 0.0 - 1.0
:Default: ``0.05``

.. _cache_target_dirty_ratio:

``cache_target_dirty_ratio``

:Description: The percentage of the cache pool containing modified (dirty)
              objects before the cache tiering agent will flush them to the
              backing storage pool.

:Type: Double
:Default: ``.4``

.. _cache_target_dirty_high_ratio:

``cache_target_dirty_high_ratio``

:Description: The percentage of the cache pool containing modified (dirty)
              objects before the cache tiering agent will flush them to the
              backing storage pool with a higher speed.

:Type: Double
:Default: ``.6``

.. _cache_target_full_ratio:

``cache_target_full_ratio``

:Description: The percentage of the cache pool containing unmodified (clean)
              objects before the cache tiering agent will evict them from the
              cache pool.

:Type: Double
:Default: ``.8``

.. _target_max_bytes:

``target_max_bytes``

:Description: Ceph will begin flushing or evicting objects when the
              ``max_bytes`` threshold is triggered.

:Type: Integer
:Example: ``1000000000000``  #1-TB

.. _target_max_objects:

``target_max_objects``

:Description: Ceph will begin flushing or evicting objects when the
              ``max_objects`` threshold is triggered.

:Type: Integer
:Example: ``1000000`` #1M objects


``hit_set_grade_decay_rate``

:Description: Temperature decay rate between two successive hit_sets
:Type: Integer
:Valid Range: 0 - 100
:Default: ``20``


``hit_set_search_last_n``

:Description: Count at most N appearance in hit_sets for temperature calculation
:Type: Integer
:Valid Range: 0 - hit_set_count
:Default: ``1``


.. _cache_min_flush_age:

``cache_min_flush_age``

:Description: The time (in seconds) before the cache tiering agent will flush
              an object from the cache pool to the storage pool.

:Type: Integer
:Example: ``600`` 10min

.. _cache_min_evict_age:

``cache_min_evict_age``

:Description: The time (in seconds) before the cache tiering agent will evict
              an object from the cache pool.

:Type: Integer
:Example: ``1800`` 30min

.. _fast_read:

``fast_read``

:Description: On Erasure Coding pool, if this flag is turned on, the read request
              would issue sub reads to all shards, and waits until it receives enough
              shards to decode to serve the client. In the case of jerasure and isa
              erasure plugins, once the first K replies return, client's request is
              served immediately using the data decoded from these replies. This
              helps to tradeoff some resources for better performance. Currently this
              flag is only supported for Erasure Coding pool.

:Type: Boolean
:Defaults: ``0``

.. _scrub_min_interval:

``scrub_min_interval``

:Description: The minimum interval in seconds for pool scrubbing when
              load is low. If it is 0, the value osd_scrub_min_interval
              from config is used.

:Type: Double
:Default: ``0``

.. _scrub_max_interval:

``scrub_max_interval``

:Description: The maximum interval in seconds for pool scrubbing
              irrespective of cluster load. If it is 0, the value
              osd_scrub_max_interval from config is used.

:Type: Double
:Default: ``0``

.. _deep_scrub_interval:

``deep_scrub_interval``

:Description: The interval in seconds for pool “deep” scrubbing. If it
              is 0, the value osd_deep_scrub_interval from config is used.

:Type: Double
:Default: ``0``


.. _recovery_priority:

``recovery_priority``

:Description: When a value is set it will increase or decrease the computed
              reservation priority. This value must be in the range -10 to
              10.  Use a negative priority for less important pools so they
              have lower priority than any new pools.

:Type: Integer
:Default: ``0``


.. _recovery_op_priority:

``recovery_op_priority``

:Description: Specify the recovery operation priority for this pool instead of ``osd_recovery_op_priority``.

:Type: Integer
:Default: ``0``


Get Pool Values
===============

To get a value from a pool, execute the following:

.. prompt:: bash $

   ceph osd pool get {pool-name} {key}

You may get values for the following keys:

``size``

:Description: see size_

:Type: Integer

``min_size``

:Description: see min_size_

:Type: Integer
:Version: ``0.54`` and above

``pg_num``

:Description: see pg_num_

:Type: Integer


``pgp_num``

:Description: see pgp_num_

:Type: Integer
:Valid Range: Equal to or less than ``pg_num``.


``crush_rule``

:Description: see crush_rule_


``hit_set_type``

:Description: see hit_set_type_

:Type: String
:Valid Settings: ``bloom``, ``explicit_hash``, ``explicit_object``

``hit_set_count``

:Description: see hit_set_count_

:Type: Integer


``hit_set_period``

:Description: see hit_set_period_

:Type: Integer


``hit_set_fpp``

:Description: see hit_set_fpp_

:Type: Double


``cache_target_dirty_ratio``

:Description: see cache_target_dirty_ratio_

:Type: Double


``cache_target_dirty_high_ratio``

:Description: see cache_target_dirty_high_ratio_

:Type: Double


``cache_target_full_ratio``

:Description: see cache_target_full_ratio_

:Type: Double


``target_max_bytes``

:Description: see target_max_bytes_

:Type: Integer


``target_max_objects``

:Description: see target_max_objects_

:Type: Integer


``cache_min_flush_age``

:Description: see cache_min_flush_age_

:Type: Integer


``cache_min_evict_age``

:Description: see cache_min_evict_age_

:Type: Integer


``fast_read``

:Description: see fast_read_

:Type: Boolean


``scrub_min_interval``

:Description: see scrub_min_interval_

:Type: Double


``scrub_max_interval``

:Description: see scrub_max_interval_

:Type: Double


``deep_scrub_interval``

:Description: see deep_scrub_interval_

:Type: Double


``allow_ec_overwrites``

:Description: see allow_ec_overwrites_

:Type: Boolean


``recovery_priority``

:Description: see recovery_priority_

:Type: Integer


``recovery_op_priority``

:Description: see recovery_op_priority_

:Type: Integer


Set the Number of Object Replicas
=================================

To set the number of object replicas on a replicated pool, execute the following:

.. prompt:: bash $

   ceph osd pool set {poolname} size {num-replicas}

.. important:: The ``{num-replicas}`` includes the object itself.
   If you want the object and two copies of the object for a total of
   three instances of the object, specify ``3``.

For example:

.. prompt:: bash $

   ceph osd pool set data size 3

You may execute this command for each pool. **Note:** An object might accept
I/Os in degraded mode with fewer than ``pool size`` replicas.  To set a minimum
number of required replicas for I/O, you should use the ``min_size`` setting.
For example:

.. prompt:: bash $

   ceph osd pool set data min_size 2

This ensures that no object in the data pool will receive I/O with fewer than
``min_size`` replicas.


Get the Number of Object Replicas
=================================

To get the number of object replicas, execute the following:

.. prompt:: bash $

   ceph osd dump | grep 'replicated size'

Ceph will list the pools, with the ``replicated size`` attribute highlighted.
By default, ceph creates two replicas of an object (a total of three copies, or
a size of 3).


.. _pgcalc: https://old.ceph.com/pgcalc/
.. _Pool, PG and CRUSH Config Reference: ../../configuration/pool-pg-config-ref
.. _Bloom Filter: https://en.wikipedia.org/wiki/Bloom_filter
.. _setting the number of placement groups: ../placement-groups#set-the-number-of-placement-groups
.. _Erasure Coding with Overwrites: ../erasure-code#erasure-coding-with-overwrites
.. _Block Device Commands: ../../../rbd/rados-rbd-cmds/#create-a-block-device-pool
