Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id C4B062E0038 for ; Tue, 6 May 2008 00:59:38 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 62281-05 for ; Tue, 6 May 2008 00:59:32 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from westnet.com (westnet.com [216.187.52.2]) by developer.postgresql.org (Postfix) with ESMTP id 7D7572E0032 for ; Tue, 6 May 2008 00:59:32 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m463xUWt004789; Mon, 5 May 2008 23:59:30 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m463xUWW004785; Mon, 5 May 2008 23:59:30 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Mon, 5 May 2008 23:59:30 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Craig James cc: pgsql-performance@postgresql.org Subject: Re: RAID 10 Benchmark with different I/O schedulers (was: Performance increase with elevator=deadline) In-Reply-To: <481F992D.7070509@emolecules.com> Message-ID: References: <47FFA7FF.10801@postnewspapers.com.au> <544D07A2-EB3F-4D91-A749-0C4D5D38AB80@gmail.com> <481F992D.7070509@emolecules.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200805/67 X-Sequence-Number: 30035 On Mon, 5 May 2008, Craig James wrote: > pgbench -i -s 20 -U test That's way too low to expect you'll see a difference in I/O schedulers. A scale of 20 is giving you a 320MB database, you can fit the whole thing in RAM and almost all of it on your controller cache. What's there to schedule? You're just moving between buffers that are generally large enough to hold most of what they need. > pgbench -c 10 -t 50000 -v -U test This is OK, because when you increase the size you're not going to be pushing 3500 TPS anymore and this test will take quite a while. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD