From 47d62c847c2ec4e54e9b7ee41878c229b183e413 Mon Sep 17 00:00:00 2001 From: Dylan Whyte Date: Thu, 18 Feb 2021 11:39:10 +0100 Subject: [PATCH] ceph: add explanation on the pg autoscaler Signed-off-by: Alwin Antreich Originally-by: Alwin Antreich Edited-by: Dylan Whyte Signed-off-by: Dylan Whyte Signed-off-by: Thomas Lamprecht --- 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 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 --------------------------- -- 2.39.2