Re: Best practice with 0.48.2 to take a node into maintenance

[David Clarke <davidc@catalyst.net.nz>]

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On 04/12/12 08:49, Christopher Kunz wrote:
> Am 03.12.12 20:14, schrieb Josh Durgin:
>> On 12/03/2012 11:05 AM, Oliver Francke wrote:
>>> Hi *,
>>> 
>>> well, even if 0.48.2 is really stable and reliable, it is not everytime the case with linux
>>> kernel. We have a couple of nodes, where an update would make life better. So, as our
>>> OSD-nodes have to care for VM's too, it's not the problem to let them drain so migrate all
>>> of them to other nodes. Just reboot? Perhaps not, cause all OSD's will begin to 
>>> remap/backfill, they are instructed to do so. Well, declare them as "osd lost"? Dangerous.
>>> Is there another way I miss in doing node-maintenance? Will we have to wait for bobtail for
>>> far less hassle with all remapping and resources?
>> 
>> By default the monitors won't mark an OSD out in the time it takes to reboot, but if
>> maintenance takes longer, you can drain data from the node.
> Hi,
> 
> what time is that (in seconds) and how can we reliably test this?

I believe that the time out you're referring to is:

'mon osd down out interval', which defaults to 300 seconds.

http://ceph.com/docs/master/rados/configuration/mon-config-ref/

Also, if you're concerned about the time it takes to reboot a machine (sans fsck) then you may
want to consider using something like kexec (kexec-tools package in Debian/Ubuntu).

http://en.wikipedia.org/wiki/Kexec


- -- 
David Clarke
Systems Architect
Catalyst IT
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