Re: Increasing # Shards vs multi-OSDs per device

[Mark Nelson <mnelson@redhat.com>]

Hi Stephen,

That's about what I expected to see, other than the write performance 
drop with more shards.  We clearly still have some room for improvement.

Good job doing the testing!

Mark

On 11/11/2015 02:57 PM, Blinick, Stephen L wrote:
> Sorry about the microphone issues in the performance meeting today today.   This is a followup to the 11/4 performance meeting where we discussed increasing the worker thread count in the OSD's vs making multiple OSD's (and partitions/filesystems) per device.     We did the high level experiment and have some results which I threw into a ppt/pdf, and shared them here:
>
> http://www.docdroid.net/UbmvGnH/increasing-shards-vs-multiple-osds.pdf.html
>
> Doing 20-shard OSD's vs 4 OSD's per device with default 5 shards yielded about half of the performance improvement for random 4k reads.  For writes performance is actually worse than just 1 OSD per device and the default # of shards.  The throttles should be large enough for the 20-shard use case as they are 10x the defaults, although if you see anything we missed let us know.
>
> I had the cluster moved to Infernalis release (with JEMalloc) yesterday, so hopefully we'll have some early results on the same 5-node cluster soon.
>
> Thanks,
>
> Stephen
>
>