X-Original-To: pgsql-performance-postgresql.org@postgresql.org Received: from localhost (mx1.hub.org [200.46.208.251]) by postgresql.org (Postfix) with ESMTP id 6243A9FB2CF for ; Tue, 15 Aug 2006 19:20:34 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.208.251]) (amavisd-new, port 10024) with ESMTP id 30098-02 for ; Tue, 15 Aug 2006 19:20:27 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey- Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id 3B1FE9FB2C5 for ; Tue, 15 Aug 2006 19:20:27 -0300 (ADT) Received: by noel.decibel.org (Postfix, from userid 1001) id 230245644A; Tue, 15 Aug 2006 17:20:26 -0500 (CDT) Received: (hashcash-sendmail, from uid 1001); Tue, 15 Aug 2006 17:20:25 -0500 Date: Tue, 15 Aug 2006 17:20:25 -0500 From: "Jim C. Nasby" To: mark@mark.mielke.cc Cc: Michael Stone , pgsql-performance@postgresql.org Subject: Re: Postgresql Performance on an HP DL385 and Message-ID: <20060815222024.GV21363@pervasive.com> References: <721b21dc0608140851v2332cdf9g59808004c983540f@mail.gmail.com> <20060814170545.GG27928@pervasive.com> <20060814170902.GN2900@mathom.us> <20060815162926.GS27928@pervasive.com> <20060815172645.GU2900@mathom.us> <20060815183327.GC12834@mark.mielke.cc> <20060815190254.GW2900@mathom.us> <20060815193951.GA13695@mark.mielke.cc> <20060815205857.GY2900@mathom.us> <20060815213842.GA15210@mark.mielke.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060815213842.GA15210@mark.mielke.cc> X-Operating-System: FreeBSD 6.0-RELEASE-p4 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.11 X-Hashcash: 1:20:060815:mark@mark.mielke.cc::TnMPYXnOmPuqYAvc:000000000000000000 0000000000000000000000003I/e X-Hashcash: 1:20:060815:mstone+postgres@mathom.us::2J9ARA94OO19h7Ey:000000000000 0000000000000000000000000JBj X-Hashcash: 1:20:060815:pgsql-performance@postgresql.org::oLdxvnHaofY137I3:00000 000000000000000000000000839P X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0.105 tagged_above=0 required=5 tests=AWL X-Spam-Level: X-Archive-Number: 200608/255 X-Sequence-Number: 20440 On Tue, Aug 15, 2006 at 05:38:43PM -0400, mark@mark.mielke.cc wrote: > I didn't know that the xlog segment only uses pre-allocated space. I > ignore mtime/atime as they don't count as file system structure > changes to me. It's updating a field in place. No change to the structure. > > With the pre-allocation knowledge, I agree with you. Not sure how I > missed that in my reviewing of the archives... I did know it > pre-allocated once upon a time... Hmm.... This is only valid if the pre-allocation is also fsync'd *and* fsync ensures that both the metadata and file data are on disk. Anyone actually checked that? :) BTW, I did see some anecdotal evidence on one of the lists a while ago. A PostgreSQL DBA had suggested doing a 'pull the power cord' test to the other DBAs (all of which were responsible for different RDBMSes, including a bunch of well known names). They all thought he was off his rocker. Not too long after that, an unplanned power outage did occur, and PostgreSQL was the only RDBMS that recovered every single database without intervention. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461