Sébastien Han
7a05ee63e4
Ceph recently changed its default PG count in https://github.com/ceph/ceph/pull/32788, it also changed from 8 to 16 then 16 to 32. So let's remove the 8 PGs mention which is incorrect. Signed-off-by: Sébastien Han <seb@redhat.com>
76 lines
3.4 KiB
Markdown
76 lines
3.4 KiB
Markdown
---
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title: Configuration
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weight: 3700
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indent: true
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---
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# Configuration
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For most any Ceph cluster, the user will want to--and may need to--change some Ceph
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configurations. These changes often may be warranted in order to alter performance to meet SLAs or
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to update default data resiliency settings.
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> **WARNING**: Modify Ceph settings carefully, and review the
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> [Ceph configuration documentation](https://docs.ceph.com/docs/master/rados/configuration/) before
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> making any changes.
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> Changing the settings could result in unhealthy daemons or even data loss if
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> used incorrectly.
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## Required configurations
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Rook and Ceph both strive to make configuration as easy as possible, but there are some
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configuration options which users are well advised to consider for any production cluster.
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### Default PG and PGP counts
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The number of PGs and PGPs can be configured on a per-pool basis, but it is highly advised to set
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default values that are appropriate for your Ceph cluster. Appropriate values depend on the number
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of OSDs the user expects to have backing each pool. The Ceph [OSD and Pool config
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docs](https://docs.ceph.com/docs/master/rados/operations/placement-groups/#a-preselection-of-pg-num)
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provide detailed information about how to tune these parameters: `osd_pool_default_pg_num` and `osd_pool_default_pgp_num`.
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Pools created prior to v1.1 will have a default PG count of 100. Pools created after v1.1
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will have Ceph's default PG count.
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An easier option exists for Rook-Ceph clusters running Ceph Nautilus (v14.2.x) or newer. Nautilus
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[introduced the PG auto-scaler mgr module](https://ceph.com/rados/new-in-nautilus-pg-merging-and-autotuning/)
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capable of automatically managing PG and PGP values for pools. This module is not enabled by default
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but can be enabled by the following setting in the [CephCluster CR](ceph-cluster-crd.md#mgr-settings):
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```yaml
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spec:
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mgr:
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modules:
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- name: pg_autoscaler
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enabled: true
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```
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With that setting, the autoscaler will be enabled for all new pools. If you do not desire to have
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the autoscaler enabled for all pools, you will need to use the Rook toolbox to enable the module
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and [enable the autoscaling](https://docs.ceph.com/docs/master/rados/operations/placement-groups/)
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on individual pools.
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## Specifying configuration options
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### Toolbox + Ceph CLI
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The most recommended way of configuring Ceph is to set Ceph's configuration directly. The first
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method for doing so is to use Ceph's CLI from the Rook-Ceph toolbox pod. Using the toolbox pod is
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detailed [here](ceph-toolbox.md). From the toolbox, the user can change Ceph configurations, enable
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manager modules, create users and pools, and much more.
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### Ceph Dashboard
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The Ceph Dashboard, examined in more detail [here](ceph-dashboard.md), is another way of setting
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some of Ceph's configuration directly. Configuration by the Ceph dashboard is recommended with the
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same priority as configuration via the Ceph CLI (above).
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### Advanced configuration via ceph.conf override ConfigMap
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Setting configs via Ceph's CLI requires that at least one mon be available for the configs to be
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set, and setting configs via dashboard requires at least one mgr to be available. Ceph may also have
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a small number of very advanced settings that aren't able to be modified easily via CLI or
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dashboard. The **least** recommended method for configuring Ceph is intended as a last-resort
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fallback in situations like these. This is covered in detail
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[here](ceph-advanced-configuration.md#custom-cephconf-settings).
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