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 3AF3E9DD733 for ; Thu, 8 Dec 2005 15:22:00 -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 35143-04 for ; Thu, 8 Dec 2005 15:21:59 -0400 (AST) X-Greylist: domain auto-whitelisted by SQLgrey- Received: from svr2.postgresql.org (svr2.postgresql.org [65.19.161.25]) by postgresql.org (Postfix) with ESMTP id 7DC259DCD83 for ; Thu, 8 Dec 2005 15:21:55 -0400 (AST) Received: from gghcwest.com (adsl-71-128-90-172.dsl.pltn13.pacbell.net [71.128.90.172]) by svr2.postgresql.org (Postfix) with ESMTP id 1ECAEF0B3A for ; Thu, 8 Dec 2005 19:21:55 +0000 (GMT) Received: from toonses.gghcwest.com (toonses.gghcwest.com [192.168.168.115]) by gghcwest.com (8.12.10/8.12.9) with ESMTP id jB8JJUmd006435; Thu, 8 Dec 2005 11:19:31 -0800 Received: from jwb by toonses.gghcwest.com with local (Exim 4.52) id 1EkRKu-0006Of-MK; Thu, 08 Dec 2005 11:21:48 -0800 Subject: Re: opinion on disk speed From: "Jeffrey W. Baker" To: Vivek Khera Cc: Postgresql Performance In-Reply-To: <3E73FEF8-DD9D-4DF7-9BB1-C020A4186296@khera.org> References: <3E73FEF8-DD9D-4DF7-9BB1-C020A4186296@khera.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Thu, 08 Dec 2005 11:21:48 -0800 Message-Id: <1134069708.24172.8.camel@toonses.gghcwest.com> Mime-Version: 1.0 X-Mailer: Evolution 2.5.2 X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0 required=5 tests=[none] X-Spam-Score: 0 X-Spam-Level: X-Archive-Number: 200512/252 X-Sequence-Number: 16073 On Thu, 2005-12-08 at 11:52 -0500, Vivek Khera wrote: > I have a choice to make on a RAID enclosure: > > 14x 36GB 15kRPM ultra 320 SCSI drives > > OR > > 12x 72GB 10kRPM ultra 320 SCSI drives > > both would be configured into RAID 10 over two SCSI channels using a > megaraid 320-2x card. > > My goal is speed. Either would provide more disk space than I would > need over the next two years. > > The database does a good number of write transactions, and a decent > number of sequential scans over the whole DB (about 60GB including > indexes) for large reports. The STR of 15k is quite a bit higher than 10k. I'd be inclined toward the 15k if it doesn't impact the budget. For the write transactions, the speed and size of the DIMM on that LSI card will matter the most. I believe the max memory on that adapter is 512MB. These cost so little that it wouldn't make sense to go with anything smaller. When comparing the two disks, don't forget to check for supported SCSI features. In the past I've been surprised that some 10k disks don't support packetization, QAS, and so forth. All 15k disks seem to support these. Don't forget to post some benchmarks when your vendor delivers ;) -jwb