mirror of https://github.com/ceph/ceph
418 lines
11 KiB
ReStructuredText
418 lines
11 KiB
ReStructuredText
=======
|
|
Pools
|
|
=======
|
|
|
|
When you first deploy a cluster without creating a pool, Ceph uses the default
|
|
pools for storing data. A pool provides you with:
|
|
|
|
- **Resilience**: You can set how many OSD are allowed to fail without loosing data.
|
|
For replicated pools, it is the desired number of copies/replicas of an object.
|
|
A typical configuration stores an object and one additional copy
|
|
(i.e., ``size = 2``), but you can determine the number of copies/replicas.
|
|
For erasure coded pools, it is the number of coding chunks
|
|
(i.e. ``m=2`` in the **erasure code profile**)
|
|
|
|
- **Placement Groups**: You can set the number of placement groups for the pool.
|
|
A typical configuration uses approximately 100 placement groups per OSD to
|
|
provide optimal balancing without using up too many computing resources. When
|
|
setting up multiple pools, be careful to ensure you set a reasonable number of
|
|
placement groups for both the pool and the cluster as a whole.
|
|
|
|
- **CRUSH Rules**: When you store data in a pool, a CRUSH ruleset mapped to the
|
|
pool enables CRUSH to identify a rule for the placement of the object
|
|
and its replicas (or chunks for erasure coded pools) in your cluster.
|
|
You can create a custom CRUSH rule for your pool.
|
|
|
|
- **Snapshots**: When you create snapshots with ``ceph osd pool mksnap``,
|
|
you effectively take a snapshot of a particular pool.
|
|
|
|
- **Set Ownership**: You can set a user ID as the owner of a pool.
|
|
|
|
To organize data into pools, you can list, create, and remove pools.
|
|
You can also view the utilization statistics for each pool.
|
|
|
|
|
|
List Pools
|
|
==========
|
|
|
|
To list your cluster's pools, execute::
|
|
|
|
ceph osd lspools
|
|
|
|
The default pools include:
|
|
|
|
- ``data``
|
|
- ``metadata``
|
|
- ``rbd``
|
|
|
|
|
|
.. _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 you Ceph configuration file, as the default is NOT ideal.
|
|
For example::
|
|
|
|
osd pool default pg num = 100
|
|
osd pool default pgp num = 100
|
|
|
|
To create a pool, execute::
|
|
|
|
ceph osd pool create {pool-name} {pg-num} [{pgp-num}] [replicated]
|
|
ceph osd pool create {pool-name} {pg-num} {pgp-num} erasure \
|
|
{erasure-code-profile}
|
|
|
|
Where:
|
|
|
|
``{pool-name}``
|
|
|
|
:Description: The name of the pool. It must be unique.
|
|
:Type: String
|
|
:Required: Yes. Picks up default or Ceph configuration value if not specified.
|
|
|
|
``{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 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
|
|
|
|
``{erasure-code-profile=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.
|
|
|
|
When you create a pool, set the number of placement groups to a reasonable value
|
|
(e.g., ``100``). Consider the total number of placement groups per OSD too.
|
|
Placement groups are computationally expensive, so performance will degrade when
|
|
you have many pools with many placement groups (e.g., 50 pools with 100
|
|
placement groups each). The point of diminishing returns depends upon the power
|
|
of the OSD host.
|
|
|
|
See `Placement Groups`_ for details on calculating an appropriate number of
|
|
placement groups for your pool.
|
|
|
|
.. _Placement Groups: ../placement-groups
|
|
|
|
|
|
Set Pool Quotas
|
|
===============
|
|
|
|
You can set pool quotas for the maximum number of bytes and/or the maximum
|
|
number of objects per pool. ::
|
|
|
|
ceph osd pool set-quota {pool-name} [max_objects {obj-count}] [max_bytes {bytes}]
|
|
|
|
For example::
|
|
|
|
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::
|
|
|
|
ceph osd pool delete {pool-name} [{pool-name} --yes-i-really-really-mean-it]
|
|
|
|
|
|
If you created your own rulesets and rules for a pool you created, you should
|
|
consider removing them when you no longer need your pool. If you created users
|
|
with permissions strictly for a pool that no longer exists, you should consider
|
|
deleting those users too.
|
|
|
|
|
|
Rename a Pool
|
|
=============
|
|
|
|
To rename a pool, execute::
|
|
|
|
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.
|
|
|
|
.. note:: Version ``0.48`` Argonaut and above.
|
|
|
|
Show Pool Statistics
|
|
====================
|
|
|
|
To show a pool's utilization statistics, execute::
|
|
|
|
rados df
|
|
|
|
|
|
Make a Snapshot of a Pool
|
|
=========================
|
|
|
|
To make a snapshot of a pool, execute::
|
|
|
|
ceph osd pool mksnap {pool-name} {snap-name}
|
|
|
|
.. note:: Version ``0.48`` Argonaut and above.
|
|
|
|
|
|
Remove a Snapshot of a Pool
|
|
===========================
|
|
|
|
To remove a snapshot of a pool, execute::
|
|
|
|
ceph osd pool rmsnap {pool-name} {snap-name}
|
|
|
|
.. note:: Version ``0.48`` Argonaut and above.
|
|
|
|
.. _setpoolvalues:
|
|
|
|
|
|
Set Pool Values
|
|
===============
|
|
|
|
To set a value to a pool, execute the following::
|
|
|
|
ceph osd pool set {pool-name} {key} {value}
|
|
|
|
You may set values for the following keys:
|
|
|
|
``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``
|
|
|
|
:Description: Sets the minimum number of replicas required for I/O.
|
|
See `Set the Number of Object Replicas`_ for further details.
|
|
Replicated pools only.
|
|
|
|
:Type: Integer
|
|
:Version: ``0.54`` and above
|
|
|
|
``crash_replay_interval``
|
|
|
|
:Description: The number of seconds to allow clients to replay acknowledged,
|
|
but uncommitted requests.
|
|
|
|
:Type: Integer
|
|
|
|
|
|
``pgp_num``
|
|
|
|
:Description: The effective number of placement groups to use when calculating
|
|
data placement.
|
|
|
|
:Type: Integer
|
|
:Valid Range: Equal to or less than ``pg_num``.
|
|
|
|
|
|
``crush_ruleset``
|
|
|
|
:Description: The ruleset to use for mapping object placement in the cluster.
|
|
:Type: Integer
|
|
|
|
|
|
``hashpspool``
|
|
|
|
:Description: Set/Unset HASHPSPOOL flag on a given pool.
|
|
:Type: Integer
|
|
:Valid Range: 1 sets flag, 0 unsets flag
|
|
:Version: Version ``0.48`` Argonaut and above.
|
|
|
|
|
|
``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``
|
|
|
|
: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``
|
|
|
|
: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``
|
|
|
|
: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``
|
|
|
|
: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_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``
|
|
|
|
:Description: Ceph will begin flushing or evicting objects when the
|
|
``max_bytes`` threshold is triggered.
|
|
|
|
:Type: Integer
|
|
:Example: ``1000000000000`` #1-TB
|
|
|
|
|
|
``target_max_objects``
|
|
|
|
:Description: Ceph will begin flushing or evicting objects when the
|
|
``max_objects`` threshold is triggered.
|
|
|
|
:Type: Integer
|
|
:Example: ``1000000`` #1M objects
|
|
|
|
|
|
``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``
|
|
|
|
:Description: The time (in seconds) before the cache tiering agent will evict
|
|
an object from the cache pool.
|
|
|
|
:Type: Integer
|
|
:Example: ``1800`` 30min
|
|
|
|
|
|
|
|
Get Pool Values
|
|
===============
|
|
|
|
To get a value from a pool, execute the following::
|
|
|
|
ceph osd pool get {pool-name} {key}
|
|
|
|
|
|
``pg_num``
|
|
|
|
:Description: The number of placement groups for the pool.
|
|
:Type: Integer
|
|
|
|
|
|
``pgp_num``
|
|
|
|
:Description: The effective number of placement groups to use when calculating data placement.
|
|
:Type: Integer
|
|
:Valid Range: Equal to or less than ``pg_num``.
|
|
|
|
|
|
Set the Number of Object Replicas
|
|
=================================
|
|
|
|
To set the number of object replicas on a replicated pool, execute the following::
|
|
|
|
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::
|
|
|
|
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::
|
|
|
|
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::
|
|
|
|
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).
|
|
|
|
|
|
|
|
.. _Pool, PG and CRUSH Config Reference: ../../configuration/pool-pg-config-ref
|
|
.. _Bloom Filter: http://en.wikipedia.org/wiki/Bloom_filter
|