Greg Smith wrote:
> On Fri, 2 Jan 2009, Tom Lane wrote:
>
> > ISTM that you *should* be able to see an improvement on even
> > single-spindle systems, due to better overlapping of CPU and I/O effort.
>
> The earlier synthetic tests I did:
>
> http://archives.postgresql.org/pgsql-hackers/2008-09/msg01401.php
>
> Showed a substantial speedup even in the single spindle case on a couple
> of systems, but one didn't really seem to benefit. So we could theorize
> that Robert's test system is more like that one. If someone can help out
> with making a more formal test case showing this in action, I'll dig into
> the details of what's different between that system and the others.
I think for an I/O-bound workload on a single drive system you would
need a drive that did some kind of tagged queuing (reordering/grouping)
of requests to see a benefit from the patch.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +