Received: from localhost (maia-3.hub.org [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id 21F4D9FB319 for ; Sun, 28 Jan 2007 19:38:26 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-new, port 10024) with ESMTP id 04663-07 for ; Sun, 28 Jan 2007 19:38:19 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 4038E9FB30F for ; Sun, 28 Jan 2007 19:38:23 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id l0SNcI2O026423; Sun, 28 Jan 2007 18:38:18 -0500 (EST) To: Josh Berkus cc: pgsql-performance@postgresql.org, "John Parnefjord" Subject: Re: Tuning In-reply-to: <200701281524.24317.josh@agliodbs.com> References: <76C73999206F3145A2E3046A5C32A103F02A5A@kibmail.kib.local> <200701281524.24317.josh@agliodbs.com> Comments: In-reply-to Josh Berkus message dated "Sun, 28 Jan 2007 15:24:24 -0800" Date: Sun, 28 Jan 2007 18:38:18 -0500 Message-ID: <26422.1170027498@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200701/398 X-Sequence-Number: 22999 Josh Berkus writes: >> -checkpoint_segments - this is crucial as one of the server is >> transaction heavy > Well, it only helps you to raise this if you have a dedicated disk resource > for the xlog. Otherwise having more segments doesn't help you much. Au contraire, large checkpoint_segments is important for write-intensive workloads no matter what your disk layout is. If it's too small then you'll checkpoint too often, and the resulting increase in page-image writes will hurt. A lot. My advice is to set checkpoint_warning to the same value as checkpoint_timeout (typically 5 minutes or so) and then keep an eye on the postmaster log for awhile. If you see more than a few "checkpoints are occuring too frequently" messages, you want to raise checkpoint_segments. regards, tom lane