doc/cephfs: add doc for disabling mgr/volumes plugin

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit 373910de34fc9e1d98218aed0361cd9bf3badffa)

diff --git a/doc/cephfs/fs-volumes.rst b/doc/cephfs/fs-volumes.rst
index 5f9405bb864e93a8b05eee0a21feafd43b07329d..3670f454e600724937aa299173b483fd8d99c643 100644 (file)
--- a/doc/cephfs/fs-volumes.rst
+++ b/doc/cephfs/fs-volumes.rst
@@ -888,5 +888,28 @@ group. This will cause every subvolume within the group to be automatically
 pinned to one of the available ranks on the file system.
 
 
+
+.. _disabling-volumes-plugin:
+
+Disabling Volumes Plugin
+------------------------
+By default the volumes plugin is enabled and set to ``always on``. However, in
+certain cases it might be appropriate to disable it. For example, when a CephFS
+is in a degraded state, the volumes plugin commands may accumulate in MGR
+instead of getting served. Which eventually causes policy throttles to kick in
+and the MGR becomes unresponsive.
+
+In this event, volumes plugin can be disabled even though it is an
+``always on`` module in MGR. To do so, run ``ceph mgr module disable volumes
+--yes-i-really-mean-it``. Do note that this command will disable operations
+and remove commands of volumes plugin since it will disable all CephFS
+services on the Ceph cluster accessed through this plugin.
+
+Before resorting to a measure as drastic as this, it is a good idea to try less
+drastic measures and then assess if the file system experience has improved due
+to it. One example of such less drastic measure is to disable asynchronous
+threads launched by volumes plugins for cloning and purging trash.
+
+
 .. _manila: https://github.com/openstack/manila
 .. _CSI: https://github.com/ceph/ceph-csi

diff --git a/doc/cephfs/troubleshooting.rst b/doc/cephfs/troubleshooting.rst
index 0e511526b96c0f72a3c4989ee0628ce44ab82598..62dd3561c47d60fe107dbda9505aedb4c90d91fd 100644 (file)
--- a/doc/cephfs/troubleshooting.rst
+++ b/doc/cephfs/troubleshooting.rst
@@ -407,6 +407,11 @@ its associated key. A less drastic but half-fix is to change the osd cap for
 your user to just ``caps osd = "allow rw"``  and delete ``tag cephfs
 data=....``
 
+Disabling Volumes Plugin
+========================
+In certain scenarios, volumes plugin might be needed to disabled to prevent compromise
+for rest of the Ceph cluster. For details see: :ref:`disabling-volumes-plugin`
+
 Reporting Issues
 ================