Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 1B0899FB277 for ; Wed, 10 Jan 2007 16:27:10 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-new, port 10024) with ESMTP id 76146-07 for ; Wed, 10 Jan 2007 16:26:51 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id C79EC9FB26B for ; Wed, 10 Jan 2007 16:26:59 -0400 (AST) Received: by noel.decibel.org (Postfix, from userid 1001) id E875356447; Wed, 10 Jan 2007 14:26:58 -0600 (CST) Received: (hashcash-sendmail, from uid 1001); Wed, 10 Jan 2007 14:26:53 -0600 Date: Wed, 10 Jan 2007 14:26:52 -0600 From: "Jim C. Nasby" To: Jeff Frost Cc: Alvaro Herrera , Ron , Guy Rouillier , PostgreSQL Performance Subject: Re: High update activity, PostgreSQL vs BigDBMS Message-ID: <20070110202652.GW12217@nasby.net> References: <45935A49.6080602@burntmail.com> <20061229220747.GB15429@alvh.no-ip.org> <20070109123312.GL12217@nasby.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 6.1-RELEASE-p10 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.13 (2006-08-11) X-Hashcash: 1:20:070110:jeff@frostconsultingllc.com::VRMUWP5rHBNAQhPR:0000000000 0000000000000000000000001RmQ X-Hashcash: 1:20:070110:alvherre@commandprompt.com::iQMDHvD+yDt+qzzi:00000000000 0000000000000000000000006YMS X-Hashcash: 1:20:070110:rjpeace@earthlink.net::5YQ7a0B68cwKsvBx:0000000000000000 0000000000000000000000004q0Y X-Hashcash: 1:20:070110:guyr-ml1@burntmail.com::oo/DMibCDkgeQeIO:000000000000000 0000000000000000000000006fPK X-Hashcash: 1:20:070110:pgsql-performance@postgresql.org::kFkRKVwwoLa72cFX:00000 0000000000000000000000005GWq X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200701/146 X-Sequence-Number: 22747 On Tue, Jan 09, 2007 at 09:10:51AM -0800, Jeff Frost wrote: > On Tue, 9 Jan 2007, Jim C. Nasby wrote: > > >On Thu, Dec 28, 2006 at 02:15:31PM -0800, Jeff Frost wrote: > >>When benchmarking various options for a new PG server at one of my > >>clients, > >>I tried ext2 and ext3 (data=writeback) for the WAL and it appeared to be > >>fastest to have ext2 for the WAL. The winning time was 157m46.713s for > >>ext2, 159m47.098s for combined ext3 data/xlog and 158m25.822s for ext3 > >>data=writeback. This was on an 8x150GB Raptor RAID10 on an Areca 1130 w/ > >>1GB BBU cache. This config benched out faster than a 6disk RAID10 + 2 > >>disk > >>RAID1 for those of you who have been wondering if the BBU write back cache > >>mitigates the need for separate WAL (at least on this workload). Those > >>are > >>the fastest times for each config, but ext2 WAL was always faster than the > >>other two options. I didn't test any other filesystems in this go around. > > > >Uh, if I'm reading this correctly, you're saying that WAL on a separate > >ext2 vs. one big ext3 with data=writeback saved ~39 seconds out of > >~158.5 minutes, or 0.4%? Is that even above the noise for your > >measurements? I suspect the phase of the moon might play a bigger role > >;P > > That's what I thought too...cept I ran it 20 times and ext2 won by that > margin every time, so it was quite repeatable. :-/ Even so, you've got to really be hunting for performance to go through the hassle of different filesystems just to gain 0.4%... :) -- Jim Nasby jim@nasby.net EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)