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 C34919DCBB6 for ; Tue, 7 Mar 2006 15:59:48 -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 15168-10 for ; Tue, 7 Mar 2006 15:59:47 -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 5A36C9DCC47 for ; Tue, 7 Mar 2006 15:59:45 -0400 (AST) Received: by noel.decibel.org (Postfix, from userid 1001) id 679C756492; Tue, 7 Mar 2006 13:59:31 -0600 (CST) Received: (hashcash-sendmail, from uid 1001); Tue, 7 Mar 2006 13:59:30 -0600 Date: Tue, 7 Mar 2006 13:59:30 -0600 From: "Jim C. Nasby" To: Joost Kraaijeveld Cc: "Pgsql-Performance (E-mail)" Subject: Re: Can anyone explain this pgbench results? Message-ID: <20060307195930.GB82989@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::x/Cv2+8yGq6oDwqk:0000000000000 0000000000000000000000004Z4X X-Hashcash: 1:20:060307:pgsql-performance@postgresql.org::Lk4Dj0R4EK7OuHzT:00000 0000000000000000000000003jn0 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: 200603/78 X-Sequence-Number: 17515 On Tue, Mar 07, 2006 at 08:49:30PM +0100, Joost Kraaijeveld wrote: > > Jim C. Nasby wrote: > > > 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? > > On a Sil SATA 3114 controller: > /dev/sda OS + Swap > /dev/sdb /var with pg_xlog > > On the 3Ware 9500S-8, 5 disk array: > /dev/sdc with the database (and very safe, my MP3 collection ;-)) > > As I wrote in one of my posts to Michael, I suspect that the card is not handling the amount of write operations as well as I expected. I wonder if anyone else sees the same characteristics with this kind of card. Well, the problem is that you're using RAID5, which has a huge write overhead. You're unlikely to get good performance with it. Also, it sounds like sda and sdb are not mirrored. If that's the case, you have no protection from a drive failure taking out your entire database, because you'd lose pg_xlog. If you want better performance your best bets are to either setup RAID10 or if you don't care about the data, just go to RAID0. -- 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