From users-return-4093-daniel=haxx.se@subversion.apache.org Tue Aug 3 17:54:29 2010 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on giant.haxx.se X-Spam-Level: X-Spam-Status: No, score=-1.5 required=3.0 tests=BAYES_00,T_RP_MATCHES_RCVD autolearn=ham version=3.3.1 Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by giant.haxx.se (8.14.3/8.14.3/Debian-9.1) with SMTP id o73FsSqa027036 for ; Tue, 3 Aug 2010 17:54:29 +0200 Received: (qmail 23772 invoked by uid 500); 3 Aug 2010 15:54:20 -0000 Mailing-List: contact users-help@subversion.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Delivered-To: mailing list users@subversion.apache.org Received: (qmail 23765 invoked by uid 99); 3 Aug 2010 15:54:20 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 03 Aug 2010 15:54:20 +0000 X-ASF-Spam-Status: No, hits=0.7 required=10.0 tests=SPF_NEUTRAL Received-SPF: neutral (athena.apache.org: local policy) Received: from [213.41.242.187] (HELO prunille.vinc17.org) (213.41.242.187) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 03 Aug 2010 15:54:14 +0000 Received: by prunille.vinc17.org (Postfix, from userid 501) id 9FD1B52CAB8C; Tue, 3 Aug 2010 17:53:52 +0200 (CEST) Date: Tue, 3 Aug 2010 17:53:52 +0200 From: Vincent Lefevre To: users@subversion.apache.org Subject: Re: Support for filesystem snapshots (?) Message-ID: <20100803155352.GJ7288@prunille.vinc17.org> Mail-Followup-To: users@subversion.apache.org References: <6EC02A00CC9F684DAF4AF4084CA84D5F01C40CBC@DRMBX3.winmail.deshaw.com> <20100802175621.GL3967@ted.stsp.name> <6EC02A00CC9F684DAF4AF4084CA84D5F01C40CD7@DRMBX3.winmail.deshaw.com> <20100802202736.GO3967@ted.stsp.name> <6EC02A00CC9F684DAF4AF4084CA84D5F01C40CE1@DRMBX3.winmail.deshaw.com> <4C5730D3.8060507@gmail.com> <82eieg56kn.fsf@mid.bfk.de> <20100803105628.GA29679@jack.stsp.name> <20100803123641.GI7288@prunille.vinc17.org> <4C5813A5.8080800@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4C5813A5.8080800@gmail.com> X-Mailer-Info: http://www.vinc17.org/mutt/ User-Agent: Mutt/1.5.20-6088-vl-r38367 (2010-07-31) X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.3.5 (giant.haxx.se [80.67.6.50]); Tue, 03 Aug 2010 17:54:29 +0200 (CEST) X-Friend: Nope On 2010-08-03 08:03:33 -0500, Les Mikesell wrote: > A filesystem snapshot should present exactly the same scenario as a > machine that lost power or crashed for some similar reason at that > moment, so the question boils down to whether subversion can recover > sensibly from a crash at any point. Not exactly: in case of a power loss or a kernel crash, the file system can become inconsistent. I think you mean something like: [...] that lost power or crashed while it wasn't writing to the disk. > The fsync's are going to be the critical thing for ordering > operations at the disk level, however there is no guarantee how much > of the fsync operation might have completed when a crash or snapshot > happens. It depends on whether the filesystem snapshot software takes kernel buffers into account or not. And one can assume that the snapshot isn't taken in the middle of a fsync. -- Vincent Lef�vre - Web: 100% accessible validated (X)HTML - Blog: Work: CR INRIA - computer arithmetic / Ar�naire project (LIP, ENS-Lyon)