>>> Christian Balzer <[email protected]> schrieb am Donnerstag, 27. Oktober 2016 um
04:07:
Hi,
> Hello,
>
> On Wed, 26 Oct 2016 15:40:00 +0000 Ashley Merrick wrote:
>
>> Hello All,
>>
>> Currently running a CEPH cluster connected to KVM via the KRBD and used only
> for this purpose.
>>
>> Is working perfectly fine, however would like to look at increasing /
> helping with random write performance and latency, specially from multiple
> VM's hitting the spinning disks at same time.
>>
> Is it more a question of contention (HDDs being busy) or latency (lots of
> small write I/Os)?
>
>> Currently have journals on SSD so helps with a very short burst, however
> looking into putting some proper SSD "cache" in front.
>>
> You will want to read some of the recent and current "cache tier" threads
> here, especially the "cache tiering deprecated in RHCS 2.0" one, to which
> interestingly there hasn't been a single comment by RH or the devs,
> official or otherwise.
>
Would the configuration of a seperat SSD only pool with corresponding crush
rules an option to overcome the "cache tier is or will be deprecated"
problematic?
So that one could use separat SSD based rbd's in qemu vm's like one would
install a mix of disks in a real PC tower (fast SSD for OS startup and datases
and
spinning disks for simple file storage).
[...]
Regards
Steffen
>
> Christian
>
>> 3/ Anything I should be aware of when looking into caching?
>>
>> Thanks for your time!,
>> Ashley
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>>
>
>
> --
> Christian Balzer Network/Systems Engineer
> [email protected] Global OnLine Japan/Rakuten Communications
> http://www.gol.com/
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