From: Scott Marlowe <scott.marlowe@gmail.com>
To: Craig James <craig_james@emolecules.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: RAID 10 Benchmark with different I/O schedulers (was: Performance increase with elevator=deadline)
Date: Mon, 5 May 2008 21:15:44 -0600
Message-ID: <dcc563d10805052015j352d71fdla2cfca22da899590@mail.gmail.com> (raw)
In-Reply-To: <481F992D.7070509@emolecules.com>
References: <D960CB61B694CF459DCFB4B0128514C201FA62C8@exadv11.host.magwien.gv.at>
<C050E63A-2209-4E89-AA99-6A327CCE7380@torgo.978.org>
<Pine.LNX.4.64.0804111736580.20402@aragorn.flymine.org>
<47FFA7FF.10801@postnewspapers.com.au>
<544D07A2-EB3F-4D91-A749-0C4D5D38AB80@gmail.com>
<481F992D.7070509@emolecules.com>
On Mon, May 5, 2008 at 5:33 PM, Craig James <craig_james@emolecules.com> wrote:
>
> (It also reinforces what the pgbench man page says: Short runs aren't
> useful. Even these two-minute runs have a lot of variability. Before I
> turned off AutoVacuum, the variability was more like 50% between runs.)
I'd suggest a couple things for more realistic tests. Run the tests
much longer, say 30 minutes to an hour. Crank up your scaling factor
until your test db is larger than memory. Turn on autovacuum, maybe
raising the cost / delay factors so it doesn't affect performance too
negatively. And lastly tuning the bgwriter so that checkpoints are
short and don't interfere too much.
My guess is if you let it run for a while, you'll get a much more
reliable number.
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, craig_james@emolecules.com
Subject: Re: RAID 10 Benchmark with different I/O schedulers (was: Performance increase with elevator=deadline)
In-Reply-To: <dcc563d10805052015j352d71fdla2cfca22da899590@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox