Re: SSD performance

On Tue, Feb 3, 2009 at 10:54 AM, Jeff <threshar(at)torgo(dot)978(dot)org> wrote:

> Now, moving into reality I compiled 8.3.latest and gave it a whirl. Running
> against a software R1 of the 2 x25-e's I got the following pgbench results:
> (note config tweaks: work_mem=>4mb, shared_buffers=>1gb, should probably
> have tweaked checkpoint_segs, as it was emitting lots of notices about that,
> but I didn't).

You may find you get better numbers with a lower shared_buffers value,
and definitely try cranking up number of checkpoint segments to
something in the 50 to 100 range.

> (multiple runs, avg tps)
>
> Scalefactor 50, 10 clients: 1700tps
>
> At that point I realized write caching on the drives was ON. So I turned it
> off at this point:
>
> Scalefactor 50, 10 clients: 900tps
>
> At scalefactor 50 the dataset fits well within memory, so I scaled it up.
>
> Scalefactor 1500: 10 clients: 420tps
>
>
> While some of us have arrays that can smash those numbers, that is crazy
> impressive for a plain old mirror pair. I also did not do much tweaking of
> PG itself.

On a scale factor or 100 my 12 disk 15k.5 seagate sas drives on an
areca get somewhere in the 2800 to 3200 tps range on sustained tests
for anywhere from 8 to 32 or so concurrent clients. I get similar
performance falloffs as I increase the testdb scaling factor.

But for a pair of disks in a mirror with no caching controller, that's
impressive. I've already told my boss our next servers will likely
have intel's SSDs in them.

> While I'm in the testing mood, are there some other tests folks would like
> me to try out?

how about varying the number of clients with a static scalefactor?

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