Received: from maia.hub.org (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id D14CB63219F for ; Tue, 16 Mar 2010 08:28:53 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 88524-09 for ; Tue, 16 Mar 2010 11:28:43 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from 27.mail-out.ovh.net (27.mail-out.ovh.net [91.121.30.210]) by mail.postgresql.org (Postfix) with SMTP id E5CEC63F246 for ; Tue, 16 Mar 2010 08:28:42 -0300 (ADT) Received: (qmail 17429 invoked by uid 503); 16 Mar 2010 11:31:45 -0000 Received: from b9.ovh.net (HELO mail626.ha.ovh.net) (213.186.33.59) by 27.mail-out.ovh.net with SMTP; 16 Mar 2010 11:31:44 -0000 Received: from b0.ovh.net (HELO queueout) (213.186.33.50) by b0.ovh.net with SMTP; 16 Mar 2010 11:29:14 -0000 Received: from par69-8-88-161-102-87.fbx.proxad.net (HELO localhost) (lists%peufeu.com@88.161.102.87) by ns0.ovh.net with SMTP; 16 Mar 2010 11:29:13 -0000 Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes To: "Greg Smith" , "Dave Crooke" Cc: "Paul McGarry" , pgsql-performance@postgresql.org Subject: Re: shared_buffers advice References: <4B9F3302.4020900@2ndquadrant.com> Date: Tue, 16 Mar 2010 12:24:40 +0100 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Pierre C" Message-ID: In-Reply-To: <4B9F3302.4020900@2ndquadrant.com> User-Agent: Opera Mail/10.10 (Linux) X-Ovh-Tracer-Id: 7748724635407222423 X-Ovh-Remote: 88.161.102.87 (par69-8-88-161-102-87.fbx.proxad.net) X-Ovh-Local: 213.186.33.20 (ns0.ovh.net) X-Spam-Check: DONE|U 0.500059/N X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-2.599 tagged_above=-10 required=5 tests=BAYES_00=-2.599 X-Spam-Level: X-Archive-Number: 201003/164 X-Sequence-Number: 37989 > -My warnings about downsides related to checkpoint issues with larger > buffer pools isn't an opinion at all; that's a fact based on limitations > in how Postgres does its checkpoints. If we get something more like > Oracle's incremental checkpoint logic, this particular concern might go > away. Does PG issue checkpoint writes in "sorted" order ? I wonder about something, too : if your DB size is smaller than RAM, you could in theory set shared_buffers to a size larger than your DB provided you still have enough free RAM left for work_mem and OS writes management. How does this interact with the logic which prevents seq-scans hogging shared_buffers ?