Received: with ECARTIS (v1.0.0; list xfs); Mon, 30 Jun 2008 06:53:52 -0700 (PDT) X-Spam-Checker-Version: SpamAssassin 3.3.0-r574664 (2007-09-11) on oss.sgi.com X-Spam-Level: X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00 autolearn=ham version=3.3.0-r574664 Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m5UDrneO030290 for ; Mon, 30 Jun 2008 06:53:49 -0700 X-ASG-Debug-ID: 1214834091-78bc03e70000-NocioJ X-Barracuda-URL: http://cuda.sgi.com:80/cgi-bin/mark.cgi Received: from mx1.redhat.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id E00D72D1F0 for ; Mon, 30 Jun 2008 06:54:51 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com [66.187.233.31]) by cuda.sgi.com with ESMTP id gDsNf2XSXZWfv0dr for ; Mon, 30 Jun 2008 06:54:51 -0700 (PDT) X-ASG-Whitelist: Barracuda Reputation Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id m5UDsZ5V007554; Mon, 30 Jun 2008 09:54:35 -0400 Received: from pobox.fab.redhat.com (pobox.fab.redhat.com [10.33.63.12]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m5UDsY2E003799; Mon, 30 Jun 2008 09:54:34 -0400 Received: from agk.fab.redhat.com (agk.fab.redhat.com [10.33.0.19]) by pobox.fab.redhat.com (8.13.1/8.13.1) with ESMTP id m5UDsYeo008044; Mon, 30 Jun 2008 09:54:34 -0400 Received: from agk by agk.fab.redhat.com with local (Exim 4.34) id 1KDJpx-0004Uc-Ta; Mon, 30 Jun 2008 14:54:33 +0100 Date: Mon, 30 Jun 2008 14:54:33 +0100 From: Alasdair G Kergon To: Takashi Sato Cc: "akpm@linux-foundation.org" , "viro@ZenIV.linux.org.uk" , "axboe@kernel.dk" , "mtk.manpages@googlemail.com" , "linux-kernel@vger.kernel.org" , "xfs@oss.sgi.com" , "dm-devel@redhat.com" , "linux-fsdevel@vger.kernel.org" , "linux-ext4@vger.kernel.org" X-ASG-Orig-Subj: Re: [dm-devel] [PATCH 0/3] freeze feature ver 1.8 Subject: Re: [dm-devel] [PATCH 0/3] freeze feature ver 1.8 Message-ID: <20080630135433.GA22522@agk.fab.redhat.com> Mail-Followup-To: Takashi Sato , "akpm@linux-foundation.org" , "viro@ZenIV.linux.org.uk" , "axboe@kernel.dk" , "mtk.manpages@googlemail.com" , "linux-kernel@vger.kernel.org" , "xfs@oss.sgi.com" , "dm-devel@redhat.com" , "linux-fsdevel@vger.kernel.org" , "linux-ext4@vger.kernel.org" References: <20080630212005t-sato@mail.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080630212005t-sato@mail.jp.nec.com> User-Agent: Mutt/1.4.1i Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE. X-Scanned-By: MIMEDefang 2.58 on 172.16.52.254 X-Barracuda-Connect: mx1.redhat.com[66.187.233.31] X-Barracuda-Start-Time: 1214834091 X-Barracuda-Virus-Scanned: by cuda.sgi.com at sgi.com X-Virus-Scanned: ClamAV 0.91.2/6021/Wed Feb 27 15:55:48 2008 on oss.sgi.com X-Virus-Status: Clean X-archive-position: 16664 X-ecartis-version: Ecartis v1.0.0 Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com X-original-sender: agk@redhat.com Precedence: bulk X-list: xfs On Mon, Jun 30, 2008 at 09:20:05PM +0900, Takashi Sato wrote: > Currently, ext3 in mainline Linux doesn't have the freeze feature which > suspends write requests. So, we cannot take a backup which keeps > the filesystem's consistency with the storage device's features > (snapshot and replication) while it is mounted. > In many case, a commercial filesystem (e.g. VxFS) has > the freeze feature and it would be used to get the consistent backup. > If Linux's standard filesytem ext3 has the freeze feature, we can do it > without a commercial filesystem. Is the following a fair summary? 1. Some filesystems have a freeze/thaw feature. XFS exports this to userspace directly through a couple of ioctls, but other filesystems don't. For filesystems on device-mapper block devices it is exported to userspace through the DM_DEV_SUSPEND ioctl which LVM uses. 2. There is a desire to access this feature from userspace on non-XFS filesystems without having to use device-mapper/LVM. Alasdair -- agk@redhat.com