Also Our Dell 400 Gb NVMe drives do not top out around 5-7 sequential writes as you mentioned. That would be 5-7 random writes from a drives perspective and the NVMe drives can do many times that.
I would park it at 5-6 partitions per NVMe , journal on the same disk. Frequently I want more concurrent operations , rather than all out throughput.
On Thu, Feb 4, 2016 at 6:49 AM Sascha Vogt <sascha.vogt@xxxxxxxxx> wrote:
Am 03.02.2016 um 17:24 schrieb Wade Holler:
> AFAIK when using XFS, parallel write as you described is not enabled.
Not sure I'm getting this. If I have multiple OSDs on the same NVMe
(separated by different data-partitions) I have multiple parallel writes
(one "stream" per OSD), or am I mistaken?
> Regardless in a way though the NVMe drives are so fast it shouldn't
> matter much the partitioned journal or other choice.
Thanks, does anyone has benchmarks on this. How about the size of the
journal?
> What I would be more interested in is you replication size on the cache
> pool.
>
> This might sound crazy but if your KVM instances are really that short
> lived, could you get away with size=2 on the cache pool from and
> availability perspective ?
:) We are already on min_size=1, size=2 - we even ran for a while witz
min_size=1, size=1, so we cannot squeeze out much more on that end.
Greetings
-Sascha-
PS: Thanks a lot already for all the answers!
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