Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id A09F89FBDF7; Fri, 30 Mar 2007 08:25:15 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-maia, port 10024) with ESMTP id 29255-07-3; Fri, 30 Mar 2007 08:25:07 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from mail01.enterprisedb.com (webmail.enterprisedb.com [63.246.7.168]) by postgresql.org (Postfix) with ESMTP id E67589FBDF0; Fri, 30 Mar 2007 08:25:11 -0300 (ADT) thread-index: AcdyvhyILX2zEjXjSdiJLCJC1Pghuw== Received: from [192.168.0.22] ([85.211.147.35]) by mail01.enterprisedb.com with Microsoft SMTPSVC(6.0.3790.1830); Fri, 30 Mar 2007 07:25:24 -0400 Content-Class: urn:content-classes:message Importance: normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.2826 Subject: Re: [PATCHES] Full page writes improvement, code update From: "Simon Riggs" To: "Richard Huxton" Cc: "Zeugswetter Andreas ADI SD" , "Koichi Suzuki" , , , In-Reply-To: <460CE5FE.5050906@archonet.com> References: <460886E8.6040907@oss.ntt.co.jp> <4609CAC3.7060008@oss.ntt.co.jp> <1175072848.4386.323.camel@silverbirch.site> <200703291145.28574.josh@agliodbs.com> <1175200117.4386.616.camel@silverbirch.site> <460C611E.6090800@oss.ntt.co.jp> <1175249717.4386.716.camel@silverbirch.site> <460CE5FE.5050906@archonet.com> Content-Type: text/plain; charset="iso-8859-1" Date: Fri, 30 Mar 2007 12:21:29 +0100 Message-ID: <1175253689.4386.749.camel@silverbirch.site> MIME-Version: 1.0 X-Mailer: Evolution 2.6.0 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 30 Mar 2007 11:25:24.0921 (UTC) FILETIME=[1C66F290:01C772BE] X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200703/1768 X-Sequence-Number: 101252 On Fri, 2007-03-30 at 11:27 +0100, Richard Huxton wrote: > Is that always true? Could the backup not pick up a partially-written > page? Assuming it's being written to as the backup is in progress. (We > are talking about when disk blocks are smaller than PG blocks here, so > can't guarantee an atomic write for a PG block?) Any page written during a backup has a backup block that would not be removable by Koichi's tool, so yes, you'd still be safe. i.e. between pg_start_backup() and pg_stop_backup() we always use full page writes, even if you are running in full_page_writes=off mode. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com