[ceph-users] Trouble removing MDS daemons | Luminous

John Spray jspray at redhat.com
Wed Nov 8 02:44:34 PST 2017


On Wed, Nov 8, 2017 at 10:39 AM, Geoffrey Rhodes <geoffrey at rhodes.org.za> wrote:
> Good day,
>
> Firstly I'd like to acknowledge that I consider myself a Ceph noob.
>
> OS: Ubuntu 16.04.3 LTS
> Ceph version: 12.2.1
>
> I'm running a small six node POC cluster with three MDS daemons. (One on
> each node,  node1, node2 and node3)
> I've also configured three ceph file systems fsys1, fsys2 and fsys3.
>
> I'd like to remove two of the file systems (fsys2 and fsys3) and at least
> one if not both of the MDS daemons.
> I was able to fail MDS on node3 using command "sudo ceph mds fail node3"
> followed by "sudo ceph mds rmfailed 0 --yes-i-really-mean-it".

When you want to remove a filesystem, you only need to do this:
ceph fs set <fs name> cluster_down true  # prevent any MDSs rejoining
the filesystem
ceph mds fail <daemon> # for each MDS that was in the filesystem
ceph fs rm <fs name> # should work because the MDSs are now no longer
involved in this filesystem.

> Then I removed the file system using command "sudo ceph fs rm fsys3
> --yes-i-really-mean-it".
>
> Running command "sudo ceph fs status" confirms that fsys3 is now failed and
> that the MDS daemon on node3 has become a standby MDS.
> I've combinations of "ceph mds (fail, deactivate, rm, rmfailed" but I can't
> seem to be able to remove the standby daemon.

You don't need to explicitly remove standby daemons using the ceph
CLI: you can just get rid of the daemon itself on the server where
it's running.  Ceph will just forget about the standby when it stops
receiving messages from that daemon.

John

> After rebooting node3 and running command "sudo ceph fs status" -  fsys3 is
> no longer a listed file system and node3 is still standby MDS.
>
> I've searched for details on this topic but what I have found has not helped
> me.
> Could anybody assist with the correct steps for removing MDS daemons and
> ceph file systems on nodes?
> It would be useful to be able to know how to completely remove all ceph file
> systems and MDS daemons should I have no further use for them in a cluster.
>
> Kind regards
> Geoffrey Rhodes
>
>
>
>
>
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