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doc/rados: add prompts to placement-groups.rst
Add unselectable prompts to doc/rados/operations/placement-groups.rst. https://tracker.ceph.com/issues/57108 Signed-off-by: Zac Dover <zac.dover@gmail.com>
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Zac Dover
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@ -20,40 +20,54 @@ Each pool has a ``pg_autoscale_mode`` property that can be set to ``off``, ``on`
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* ``on``: Enable automated adjustments of the PG count for the given pool.
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* ``warn``: Raise health alerts when the PG count should be adjusted
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To set the autoscaling mode for an existing pool::
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To set the autoscaling mode for an existing pool:
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ceph osd pool set <pool-name> pg_autoscale_mode <mode>
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.. prompt:: bash #
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For example to enable autoscaling on pool ``foo``::
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ceph osd pool set <pool-name> pg_autoscale_mode <mode>
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ceph osd pool set foo pg_autoscale_mode on
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For example to enable autoscaling on pool ``foo``:
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.. prompt:: bash #
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ceph osd pool set foo pg_autoscale_mode on
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You can also configure the default ``pg_autoscale_mode`` that is
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set on any pools that are subsequently created::
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set on any pools that are subsequently created:
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ceph config set global osd_pool_default_pg_autoscale_mode <mode>
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.. prompt:: bash #
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ceph config set global osd_pool_default_pg_autoscale_mode <mode>
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You can disable or enable the autoscaler for all pools with
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the ``noautoscale`` flag. By default this flag is set to be ``off``,
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but you can turn it ``on`` by using the command::
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but you can turn it ``on`` by using the command:
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ceph osd pool set noautoscale
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.. prompt:: bash $
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You can turn it ``off`` using the command::
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ceph osd pool set noautoscale
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ceph osd pool unset noautoscale
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You can turn it ``off`` using the command:
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To ``get`` the value of the flag use the command::
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.. prompt:: bash #
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ceph osd pool get noautoscale
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ceph osd pool unset noautoscale
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To ``get`` the value of the flag use the command:
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.. prompt:: bash #
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ceph osd pool get noautoscale
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Viewing PG scaling recommendations
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----------------------------------
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You can view each pool, its relative utilization, and any suggested changes to
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the PG count with this command::
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the PG count with this command:
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ceph osd pool autoscale-status
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.. prompt:: bash #
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ceph osd pool autoscale-status
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Output will be something like::
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@ -103,7 +117,9 @@ change is in progress). **NEW PG_NUM**, if present, is what the
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system believes the pool's ``pg_num`` should be changed to. It is
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always a power of 2, and will only be present if the "ideal" value
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varies from the current value by more than a factor of 3 by default.
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This factor can be be adjusted with::
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This factor can be be adjusted with:
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.. prompt:: bash #
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ceph osd pool set threshold 2.0
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@ -152,9 +168,11 @@ than a factor of 3 off from what it thinks it should be.
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The target number of PGs per OSD is based on the
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``mon_target_pg_per_osd`` configurable (default: 100), which can be
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adjusted with::
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adjusted with:
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ceph config set global mon_target_pg_per_osd 100
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.. prompt:: bash #
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ceph config set global mon_target_pg_per_osd 100
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The autoscaler analyzes pools and adjusts on a per-subtree basis.
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Because each pool may map to a different CRUSH rule, and each rule may
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@ -179,17 +197,23 @@ scales down when the usage ratio across the pool is not even.
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However, if the pool doesn't have the `bulk` flag, the pool will
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start out with minimal PGs and only when there is more usage in the pool.
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To create pool with `bulk` flag::
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To create pool with `bulk` flag:
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ceph osd pool create <pool-name> --bulk
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.. prompt:: bash #
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To set/unset `bulk` flag of existing pool::
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ceph osd pool create <pool-name> --bulk
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ceph osd pool set <pool-name> bulk <true/false/1/0>
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To set/unset `bulk` flag of existing pool:
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To get `bulk` flag of existing pool::
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.. prompt:: bash #
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ceph osd pool get <pool-name> bulk
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ceph osd pool set <pool-name> bulk <true/false/1/0>
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To get `bulk` flag of existing pool:
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.. prompt:: bash #
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ceph osd pool get <pool-name> bulk
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.. _specifying_pool_target_size:
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@ -210,14 +234,18 @@ The *target size* of a pool can be specified in two ways: either in
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terms of the absolute size of the pool (i.e., bytes), or as a weight
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relative to other pools with a ``target_size_ratio`` set.
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For example::
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For example:
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ceph osd pool set mypool target_size_bytes 100T
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.. prompt:: bash #
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ceph osd pool set mypool target_size_bytes 100T
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will tell the system that `mypool` is expected to consume 100 TiB of
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space. Alternatively::
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space. Alternatively:
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ceph osd pool set mypool target_size_ratio 1.0
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.. prompt:: bash #
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ceph osd pool set mypool target_size_ratio 1.0
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will tell the system that `mypool` is expected to consume 1.0 relative
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to the other pools with ``target_size_ratio`` set. If `mypool` is the
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@ -244,10 +272,12 @@ parallelism client will see when doing IO, even when a pool is mostly
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empty. Setting the lower bound prevents Ceph from reducing (or
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recommending you reduce) the PG number below the configured number.
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You can set the minimum or maximum number of PGs for a pool with::
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You can set the minimum or maximum number of PGs for a pool with:
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ceph osd pool set <pool-name> pg_num_min <num>
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ceph osd pool set <pool-name> pg_num_max <num>
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.. prompt:: bash #
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ceph osd pool set <pool-name> pg_num_min <num>
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ceph osd pool set <pool-name> pg_num_max <num>
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You can also specify the minimum or maximum PG count at pool creation
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time with the optional ``--pg-num-min <num>`` or ``--pg-num-max
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@ -258,9 +288,11 @@ time with the optional ``--pg-num-min <num>`` or ``--pg-num-max
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A preselection of pg_num
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========================
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When creating a new pool with::
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When creating a new pool with:
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ceph osd pool create {pool-name} [pg_num]
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.. prompt:: bash #
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ceph osd pool create {pool-name} [pg_num]
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it is optional to choose the value of ``pg_num``. If you do not
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specify ``pg_num``, the cluster can (by default) automatically tune it
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@ -269,7 +301,7 @@ for you based on how much data is stored in the pool (see above, :ref:`pg-autosc
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Alternatively, ``pg_num`` can be explicitly provided. However,
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whether you specify a ``pg_num`` value or not does not affect whether
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the value is automatically tuned by the cluster after the fact. To
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enable or disable auto-tuning::
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enable or disable auto-tuning:
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ceph osd pool set {pool-name} pg_autoscale_mode (on|off|warn)
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