X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 813B59DCC40 for ; Tue, 7 Mar 2006 15:09:38 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 05835-07 for ; Tue, 7 Mar 2006 15:09:38 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id 466E39DCC60 for ; Tue, 7 Mar 2006 15:09:34 -0400 (AST) Received: by noel.decibel.org (Postfix, from userid 1001) id EA0AA5646A; Tue, 7 Mar 2006 13:09:34 -0600 (CST) Received: (hashcash-sendmail, from uid 1001); Tue, 7 Mar 2006 13:09:34 -0600 Date: Tue, 7 Mar 2006 13:09:34 -0600 From: "Jim C. Nasby" To: Joost Kraaijeveld Cc: "Pgsql-Performance (E-mail)" Subject: Re: Can anyone explain this pgbench results? Message-ID: <20060307190933.GY82989@pervasive.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 6.0-RELEASE-p4 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.11 X-Hashcash: 1:20:060307:j.kraaijeveld@askesis.nl::yt1u2OYai4axlgNU:0000000000000 0000000000000000000000004uZS X-Hashcash: 1:20:060307:pgsql-performance@postgresql.org::MxPCMZu4yTLVfrU2:00000 0000000000000000000000005gHg X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.109 required=5 tests=[AWL=0.109] X-Spam-Score: 0.109 X-Spam-Level: X-Archive-Number: 200603/72 X-Sequence-Number: 17509 On Mon, Mar 06, 2006 at 04:29:49PM +0100, Joost Kraaijeveld wrote: > I was expecting a low(ish) score the first run (because the tables are not loaded in the cache yet), followed by continues high(ish) scores, but not an alternating pattern. I also did not expect so much difference, given the hardware I have (Dual Opteron, 4GB memory , 3Ware SATA RAID5 with 5 disks, seerate swap and pg_log disks). On a side-note: RAID5 and databases generally don't mix well. Most people find that pg_xlog will live happily with the OS; it's the data files that need the most bandwidth. If you start swapping, performance will tank to the point that it's unlikely that swap being on seperate disks will help at all. Better off to just keep it with the OS and use the disks for the database tables. Speaking of 'disks', what's your exact layout? Do you have a 5 drive raid5 for the OS and the database, 1 drive for swap and 1 drive for pg_xlog? -- Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461