Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 1E460650E88 for ; Wed, 25 Jun 2008 12:45:49 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 03024-05 for ; Wed, 25 Jun 2008 12:45:45 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from westnet.com (westnet.com [216.187.52.2]) by postgresql.org (Postfix) with ESMTP id 16C20650EA3 for ; Wed, 25 Jun 2008 12:45:45 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m5PFjhB5018018; Wed, 25 Jun 2008 11:45:43 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m5PFjhCU018011; Wed, 25 Jun 2008 11:45:43 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Wed, 25 Jun 2008 11:45:43 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Henrik cc: pgsql-performance@postgresql.org Subject: Re: Hardware suggestions for high performance 8.3 In-Reply-To: Message-ID: References: <2B6702BC-3513-407E-AAC2-7E04299CA237@mac.se> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200806/142 X-Sequence-Number: 30492 On Wed, 25 Jun 2008, Henrik wrote: > Would you turn off fsync if you had a controller with BBU? =) Turning off fsync has some potential to introduce problems even in that environment, so better not to do that. The issue is that you might have, say, 1GB of OS-level cache but 256MB of BBU cache, and if you turn fsync off it won't force the OS cache out to the controller when it's supposed to and that can cause corruption. Also, if you've got a controller with BBU, the overhead of fsync for regular writes is low enough that you don't really need to turn it off. If writes are cached the fsync is almost free. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD