Received: from localhost (unknown [200.46.204.184]) by developer.postgresql.org (Postfix) with ESMTP id 693822E004E for ; Tue, 6 May 2008 17:35:10 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-maia, port 10024) with ESMTP id 91669-03 for ; Tue, 6 May 2008 17:35:00 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from westnet.com (westnet.com [216.187.52.2]) by developer.postgresql.org (Postfix) with ESMTP id B80CD2E003C for ; Tue, 6 May 2008 17:35:04 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m46KZ2jU022398; Tue, 6 May 2008 16:35:02 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m46KZ2ZZ022393; Tue, 6 May 2008 16:35:02 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Tue, 6 May 2008 16:35:02 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Dennis Muhlestein cc: pgsql-performance@postgresql.org Subject: Re: Possible Redundancy/Performance Solution In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200805/107 X-Sequence-Number: 30075 On Tue, 6 May 2008, Dennis Muhlestein wrote: > I was planning on pgpool being the cushion between the raid0 failure > probability and my need for redundancy. This way, I get protection against > not only disks, but cpu, memory, network cards,motherboards etc. Is this > not a reasonable approach? Since disks are by far the most likely thing to fail, I think it would be bad planning to switch to a design that doubles the chance of a disk failure taking out the server just because you're adding some server-level redundancy. Anybody who's been in this business for a while will tell you that seemingly improbable double failures happen, and if were you'd I want a plan that survived a) a single disk failure on the primary and b) a single disk failure on the secondary at the same time. Let me strengthen that--I don't feel comfortable unless I'm able to survive a single disk failure on the primary and complete loss of the secondary (say by power supply failure), because a double failure that starts that way is a lot more likely than you might think. Especially with how awful hard drives are nowadays. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD