When rebooting a server if it takes too long to come back up then the osds will get marked out and data will start backfilling to replace the copies on the osds that are no longer "in" in the cluster.
Once those osds come back, not only do they need to backfill to catch up on what they missed while they were down, but the cluster now needs to undo all of the data migration it was doing to recover from them being marked out.
On Tue, Feb 27, 2018, 4:24 PM John Spray <jspray@xxxxxxxxxx> wrote:
On Tue, Feb 27, 2018 at 6:37 PM, Andre Goree <andre@xxxxxxxxxx> wrote:
> Is it still considered best practice to set 'noout' for OSDs that will be
> going under maintenance, e.g., rebooting an OSD ndoe for a kernel update?
>
> I ask, because I've set this twice now during times which the OSDs would
> only momentarily be 'out', however each time I've done this, the OSDs have
> become unusable and I've had to rebuild them.
Can you be more specific about "unusable"? Marking an OSD noout is of
course not meant to harm it!
John
> Also, when I _do not_ set 'noout', it would seem that once the node reboots
> the OSDs come back online without issue _and_ there is very _little_
> recovery i/o -- I'd expect to see lots of recovery i/o if a node goes down
> as the cluster tries to replace the PGs on other OSD nodes. This further
> makes me believe that setting 'noout' is no longer necessary.
>
> I'm running version 12.2.2-12.2.4 (in the middle of upgrading).
>
> Thanks in advance.
>
> --
> Andre Goree
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