| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Craig James <cjames(at)emolecules(dot)com> |
| Cc: | Evgeny Shishkin <itparanoia(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Two identical systems, radically different performance |
| Date: | 2012-10-08 23:12:54 |
| Message-ID: | CAGTBQpYZv-fSWx1xaDxkJrE1Vo-SvNKPCjH2JXNdhY0vLH3iRA@mail.gmail.com |
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| Lists: | pgsql-performance |
On Mon, Oct 8, 2012 at 8:03 PM, Craig James <cjames(at)emolecules(dot)com> wrote:
>> > But again ... the two systems are identical. This can't explain it.
>>
>> Is the read-ahead the same in both systems?
>
>
> Yes, as I said in the original reply (it got cut off from your reply): "Same
> on both servers."
Oh, yes. Google collapsed it. Wierd.
Anyway, sequential I/O isn't the same in both servers, and usually you
don't get full sequential performance unless you bump up the
read-ahead. I'm still betting on that for the difference in sequential
performance.
As for pgbench, I'm not sure, but I think pgbench doesn't really
stress sequential performance. You seem to be getting bad queueing
performance. Did you check NCQ status on the RAID controller? Is it on
on both servers?
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