On 20/12/13 13:51, Sage Weil wrote:
> On Thu, 19 Dec 2013, John-Paul Robinson wrote:
>> What impact does rebooting nodes in a ceph cluster have on the health of
>> the ceph cluster? Can it trigger rebalancing activities that then have
>> to be undone once the node comes back up?
>>
>> I have a 4 node ceph cluster each node has 11 osds. There is a single
>> pool with redundant storage.
>>
>> If it takes 15 minutes for one of my servers to reboot is there a risk
>> that some sort of needless automatic processing will begin?
>
> By default, we start rebalancing data after 5 minutes. You can adjust
> this (to, say, 15 minutes) with
>
> mon osd down out interval = 900
>
> in ceph.conf.
>
> sage
>
>>
>> I'm assuming that the ceph cluster can go into a "not ok" state but that
>> in this particular configuration all the data is protected against the
>> single node failure and there is no place for the data to migrate too so
>> nothing "bad" will happen.
>>
>> Thanks for any feedback.
Not directly related to Ceph, but you may want to investigate kexec[0] ('kexec-tools' package in
Debian derived distributions) in order to get your machines rebooting quicker. It essentially
re-loads the kernel as the last step of the shutdown procedure, skipping over the lengthy
BIOS/UEFI/controller firmware etc boot stages.
[0]: http://en.wikipedia.org/wiki/Kexec
--
David Clarke
Systems Architect
Catalyst IT
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