Received: from localhost (unknown [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id DDD719F9C11 for ; Tue, 11 Sep 2007 18:26:48 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-maia, port 10024) with ESMTP id 94519-02 for ; Tue, 11 Sep 2007 18:26:39 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id 01C8A9FA066 for ; Tue, 11 Sep 2007 18:26:43 -0300 (ADT) Received: by noel.decibel.org (Postfix, from userid 1001) id A46A456503; Tue, 11 Sep 2007 21:26:41 +0000 (UTC) Received: (hashcash-sendmail, from uid 1001); Tue, 11 Sep 2007 16:26:34 -0500 Date: Tue, 11 Sep 2007 16:26:34 -0500 From: Decibel! To: Mark Mielke Cc: Scott Marlowe , Gregory Stark , Luke Lonergan , Carlo Stonebanks , pgsql-performance@postgresql.org Subject: Re: random_page_costs - are defaults of 4.0 realistic for SCSI RAID 1 Message-ID: <20070911212634.GE38801@decibel.org> References: <87y7fekxga.fsf@oxford.xeocode.com> <46E5C38E.8030806@mark.mielke.cc> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="QYlBZwq81ScPEkIs" Content-Disposition: inline In-Reply-To: <46E5C38E.8030806@mark.mielke.cc> X-Operating-System: FreeBSD 6.1-RELEASE-p10 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.13 (2006-08-11) X-Hashcash: 1:20:070911:mark@mark.mielke.cc::1zDyz592abzTNe/d:000000000000000000 00000000000000000000000020gv X-Hashcash: 1:20:070911:scott.marlowe@gmail.com::2DZICCWZhOEkxNrZ:00000000000000 0000000000000000000000000ZAi X-Hashcash: 1:20:070911:stark@enterprisedb.com::E3dnBmlIeYQGJ6Gr:000000000000000 0000000000000000000000000jMv X-Hashcash: 1:20:070911:llonergan@greenplum.com::bJZWoLar2Y2b8EyH:00000000000000 0000000000000000000000008SWY X-Hashcash: 1:20:070911:stonec.register@sympatico.ca::dCodHCGAKTar6A5E:000000000 00000000000000000000000026Wi X-Hashcash: 1:20:070911:pgsql-performance@postgresql.org::qnhaCvY7vTCHiUCZ:00000 0000000000000000000000009wdl X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200709/202 X-Sequence-Number: 26747 --QYlBZwq81ScPEkIs Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 10, 2007 at 06:22:06PM -0400, Mark Mielke wrote: > In my case, I set effective_cache_size to 25% of the RAM available to=20 > the system (256 Mbytes), for a database that was about 100 Mbytes or=20 > less. I found performance to increase when reducing random_page_cost=20 > from 4.0 to 3.0. Just for the record, effective_cache_size of 25% is *way* too low in most cases, though if you only have 1GB setting it to 500MB probably isn't too far off. Generally, I'll set this to however much memory is in the server, minus 1G for the OS, unless there's less than 4G of total memory in which case I subtract less. --=20 Decibel!, aka Jim Nasby decibel@decibel.org EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) --QYlBZwq81ScPEkIs Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.3 (FreeBSD) iD8DBQFG5wgKdO30qud8SkgRAiapAJ9DWHWIADgOKOoNrs5WW1HZ3K7kNACeJ+1x GUcWMPM0DTDUAoKQEzapahw= =N7pS -----END PGP SIGNATURE----- --QYlBZwq81ScPEkIs--