Thank's Kurt,
That's comfort me in my decision to separate OS and Journal.
Martin
Martin Catudal
Responsable TIC
Ressources Metanor Inc
Ligne directe: (819) 218-2708
Le 2013-10-24 10:40, Kurt Bauer a écrit :
> Hi,
>
> we had a setup like this and ran into trouble, so I would strongly
> discourage you from setting it up like this. Under normal circumstances
> there's no problem, but when the cluster is under heavy load, for
> example when it has a lot of pgs backfilling, for whatever reason
> (increasing num of pgs, adding OSDs,..), there's obviously a lot of
> entries written to the journals.
> What we saw then was extremly laggy behavior of the cluster and when
> looking at the iostats of the SSD, they were at 100% most of the time. I
> don't exactly know what causes this and why the SSDs can't cope with the
> amount of IOs, but seperating OS and journals did the trick. We now have
> quick 15k HDDs in Raid1 for OS and Monitor journal and per 5 OSD
> journals one SSD with one partition per journal (used as raw partition).
>
> Hope that helps,
> best regards,
> Kurt
>
> Martin Catudal schrieb:
>> Hi,
>> Here my scenario :
>> I will have a small cluster (4 nodes) with 4 (4 TB) OSD's per node.
>>
>> I will have OS installed on two SSD in raid 1 configuration.
>>
>> Is one of you have successfully and efficiently a Ceph cluster that is
>> built with Journal on a separate partition on the OS SSD's?
>>
>> I know that it may occur a lot of IO on the Journal SSD and I'm scared
>> of have my OS suffer from too much IO.
>>
>> Any background experience?
>>
>> Martin
>>
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