Replace OSD drive without remove/re-add OSD

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On Sat, May 3, 2014 at 4:01 AM, Indra Pramana <indra at sg.or.id> wrote:
> Sorry forgot to cc the list.
>
> On 3 May 2014 08:00, "Indra Pramana" <indra at sg.or.id> wrote:
>>
>> Hi Andrey,
>>
>> I actually wanted to try this (instead of remove and readd OSD) to avoid
>> remapping of PGs to other OSDs and the unnecessary I/O load.
>>
>> Are you saying that doing this will also trigger remapping? I thought it
>> will just do recovery to replace missing PGs as a result of the drive
>> replacement?
>>
>> Thank you.
>>

Yes, remapping will take place, though it is a bit counterintuitive
and I suspect that the roots are the same as with double data
placement recalculation with out + rm procedure. Actually Inktank
people may answer the question with more details I suppose. Also I
think that preserving of the collections may eliminate remap during
such kind of refill, though it is not trivial thing to do and I had
not experimented with this.

>> On 2 May 2014 21:02, "Andrey Korolyov" <andrey at xdel.ru> wrote:
>>>
>>> On 05/02/2014 03:27 PM, Indra Pramana wrote:
>>> > Hi,
>>> >
>>> > May I know if it's possible to replace an OSD drive without removing /
>>> > re-adding back the OSD? I want to avoid the time and the excessive I/O
>>> > load which will happen during the recovery process at the time when:
>>> >
>>> > - the OSD is removed; and
>>> > - the OSD is being put back into the cluster.
>>> >
>>> > I read David Zafman's comment on this thread, that we can set "noout",
>>> > take OSD "down", replace the drive, and then bring the OSD back "up"
>>> > and
>>> > unset "noout".
>>> >
>>> > http://www.spinics.net/lists/ceph-users/msg05959.html
>>> >
>>> > May I know if it's possible to do this?
>>> >
>>> > - ceph osd set noout
>>> > - sudo stop ceph-osd id=12
>>> > - Replace the drive, and once done:
>>> > - sudo start ceph-osd id=12
>>> > - ceph osd unset noout
>>> >
>>> > The cluster was built using ceph-deploy, can we just replace a drive
>>> > like that without zapping and preparing the disk using ceph-deploy?
>>> >
>>>
>>> There will be absolutely no quirks except continuous remapping with
>>> peering along entire recovery process. If your cluster may meet this
>>> well, there is absolutely no problem to go through this flow. Otherwise,
>>> in longer out+in flow, there are only two short intensive recalculations
>>> which can be done at the scheduled time, comparing with peering during
>>> remap, which can introduce unnecessary I/O spikes.
>>>
>>> > Looking forward to your reply, thank you.
>>> >
>>> > Cheers.
>>> >
>>> >
>>> > _______________________________________________
>>> > ceph-users mailing list
>>> > ceph-users at lists.ceph.com
>>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>> >
>>>
>


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