Received: from localhost (maia-5.hub.org [200.46.204.182]) by postgresql.org (Postfix) with ESMTP id 7B8079FBC3A; Fri, 30 Mar 2007 08:48:52 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.182]) (amavisd-maia, port 10024) with ESMTP id 79186-01; Fri, 30 Mar 2007 08:48:44 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from mail.metronet.co.uk (mail.metronet.co.uk [213.162.97.75]) by postgresql.org (Postfix) with ESMTP id 1F1029FBBE1; Fri, 30 Mar 2007 08:48:49 -0300 (ADT) Received: from server3.office.archonet.com (84-51-143-99.archon037.adsl.metronet.co.uk [84.51.143.99]) by smtp.metronet.co.uk (MetroNet Mail) with ESMTP id C0FBD144586; Fri, 30 Mar 2007 12:48:47 +0100 (BST) Received: from [192.168.1.36] (dell36.office.archonet.com [192.168.1.36]) by server3.office.archonet.com (Postfix) with ESMTP id A9CEC27408E; Fri, 30 Mar 2007 12:48:47 +0100 (BST) Message-ID: <460CF91F.8040904@archonet.com> Date: Fri, 30 Mar 2007 12:48:47 +0100 From: Richard Huxton User-Agent: IceDove 1.5.0.9 (X11/20061220) MIME-Version: 1.0 To: Simon Riggs Cc: Zeugswetter Andreas ADI SD , Koichi Suzuki , josh@agliodbs.com, pgsql-hackers@postgresql.org, pgsql-patches@postgresql.org Subject: Re: [PATCHES] Full page writes improvement, code update 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> <1175253689.4386.749.camel@silverbirch.site> In-Reply-To: <1175253689.4386.749.camel@silverbirch.site> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200703/1770 X-Sequence-Number: 101254 Simon Riggs wrote: > 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. Ah, that's OK then. -- Richard Huxton Archonet Ltd