From: Dylan Whyte <d.whyte@proxmox.com>
To: pve-devel@lists.proxmox.com
Subject: [pve-devel] [PATCH v2 pve-docs 2/2] ceph: add explanation on the pg autoscaler
Date: Thu, 18 Feb 2021 11:39:10 +0100 [thread overview]
Message-ID: <20210218103910.21127-2-d.whyte@proxmox.com> (raw)
In-Reply-To: <20210218103910.21127-1-d.whyte@proxmox.com>
Signed-off-by: Alwin Antreich
edited-by: Dylan Whyte <d.whyte@proxmox.com>
---
v1->v2:
* minor language fixup
pveceph.adoc | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/pveceph.adoc b/pveceph.adoc
index 9253613..9ef268b 100644
--- a/pveceph.adoc
+++ b/pveceph.adoc
@@ -540,6 +540,42 @@ pveceph pool destroy <name>
NOTE: Deleting the data of a pool is a background task and can take some time.
You will notice that the data usage in the cluster is decreasing.
+
+PG Autoscaler
+~~~~~~~~~~~~~
+
+The PG autoscaler allows the cluster to consider the amount of (expected) data
+stored in each pool and to choose the appropriate pg_num values automatically.
+
+You may need to activate the PG autoscaler module before adjustments can take
+effect.
+[source,bash]
+----
+ceph mgr module enable pg_autoscaler
+----
+
+The autoscaler is configured on a per pool basis and has the following modes:
+
+[horizontal]
+warn:: A health warning is issued if the suggested `pg_num` value differs too
+much from the current value.
+on:: The `pg_num` is adjusted automatically with no need for any manual
+interaction.
+off:: No automatic `pg_num` adjustments are made, and no warning will be issued
+if the PG count is far from optimal.
+
+The scaling factor can be adjusted to facilitate future data storage, with the
+`target_size`, `target_size_ratio` and the `pg_num_min` options.
+
+WARNING: By default, the autoscaler considers tuning the PG count of a pool if
+it is off by a factor of 3. This will lead to a considerable shift in data
+placement and might introduce a high load on the cluster.
+
+You can find a more in-depth introduction to the PG autoscaler on Ceph's Blog -
+https://ceph.io/rados/new-in-nautilus-pg-merging-and-autotuning/[New in
+Nautilus: PG merging and autotuning].
+
+
[[pve_ceph_device_classes]]
Ceph CRUSH & device classes
---------------------------
--
2.20.1
next prev parent reply other threads:[~2021-02-18 10:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-18 10:39 [pve-devel] [PATCH v2 pve-docs 1/2] docs: ceph: explain pool options Dylan Whyte
2021-02-18 10:39 ` Dylan Whyte [this message]
2021-02-25 18:29 ` [pve-devel] applied: [PATCH v2 pve-docs 2/2] ceph: add explanation on the pg autoscaler Thomas Lamprecht
2021-02-25 18:29 ` [pve-devel] applied: [PATCH v2 pve-docs 1/2] docs: ceph: explain pool options Thomas Lamprecht
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