Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 06CF59F9250 for ; Thu, 8 Nov 2007 16:31:30 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 70792-10 for ; Thu, 8 Nov 2007 16:31:20 -0400 (AST) Received: from gwmta.wicourts.gov (gwmta.wicourts.gov [165.219.244.99]) by postgresql.org (Postfix) with ESMTP id 316CA9F9248 for ; Thu, 8 Nov 2007 16:31:18 -0400 (AST) Received: from Courts-MTA by gwmta.wicourts.gov with Novell_GroupWise; Thu, 08 Nov 2007 14:31:15 -0600 Message-Id: <47331DA7.EE98.0025.0@wicourts.gov> X-Mailer: Novell GroupWise Internet Agent 7.0.2 Date: Thu, 08 Nov 2007 14:31:04 -0600 From: "Kevin Grittner" To: "Dimitri Fontaine" , Cc: "Scott Marlowe" , "Vivek Khera" Subject: Re: dell versus hp References: <82607932-FC46-4B73-BF78-2290EE55F7F5@pvv.ntnu.no> <44B74F2E-29A6-4746-B8A8-E9355CC2F527@kcilink.com> <200711082114.36788.dfontaine@hi-media.com> In-Reply-To: <200711082114.36788.dfontaine@hi-media.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200711/112 X-Sequence-Number: 27527 >>> On Thu, Nov 8, 2007 at 2:14 PM, in message <200711082114.36788.dfontaine@hi-media.com>, Dimitri Fontaine wrote:=20 =20 > The Dell 2900 5U machine has 10 spindles max, that would make 2 for the = OS=20 > (raid1) and 8 for mixing WAL and data... not enough to benefit from = the=20 > move,=20 > or still to test? =20 From our testing and various posts on the performance list, you can expect a good battery backed caching RAID controller will probably eliminate most of the performance difference between separate WAL drives and leaving them on the same RAID array with the rest of the database. See, for example: =20 http://archives.postgresql.org/pgsql-performance/2007-02/msg00026.php =20 Ben found a difference of "a few percent"; I remember seeing a post from someone who did a lot of testing and found a difference of 1%. As stated in the above referenced posting, it will depend on your workload (and your hardware) so it is best if you can do some realistic tests. =20 -Kevin =20