maas-devel team mailing list archive

[Stuart Bishop <stuart.bishop@xxxxxxxxxxxxx>]

On Tue, Oct 16, 2012 at 9:13 PM, John Arbash Meinel
<john@xxxxxxxxxxxxxxxxx> wrote:

> So you can see that we can do 2 tags at one time, but beyond that we
> just serialize the requests. (Which makes sense, because each cluster
> only has 2 workers for 2 cpus. I do wonder if we could overcommit
> because we should be spending some time waiting for the other side to
> think.)

A rule of thumb is to allow (#cores +  #drives) x idle% simultaneous
requests. So an 8 core system writing to 5 mirrored drives where we
find that 20% of the time the db connections are idle (waiting for
client side processing) (8+5)*1.2 =16 simultaneous requests. It is
interesting that you don't see a benefit beyond just #cores. Are you
are benchmarking a read heavy operation? If you are not having to
worry about the disk subsystem, with PG 9.1  you should scale up to 24
cores reasonably happily, and PG 9.2 64 cores.

PG 9.2 has now been released - It would be interesting to see results
if you dropped that in. You won't be shipping with 9.2 yet, but there
are changes in 9.2 that could significantly speed things up.

-- 
Stuart Bishop <stuart.bishop@xxxxxxxxxxxxx>