From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.12.11.20060308/8.12.11) with ESMTP id k9ALPIjl027459 for ; Tue, 10 Oct 2006 17:25:18 -0400 Received: from broaderband.net ([82.153.231.242]) by mx1.redhat.com (8.12.11.20060308/8.12.11) with ESMTP id k9ALPGaL025808 for ; Tue, 10 Oct 2006 17:25:16 -0400 Received: from localhost ([127.0.0.1]) by broaderband.net with esmtp (Exim 4.20) id 1GXNku-0002MY-NV for linux-lvm@redhat.com; Tue, 10 Oct 2006 20:59:12 +0100 Message-ID: <452BFBF9.3060301@overnetdata.com> Date: Tue, 10 Oct 2006 21:00:57 +0100 From: Anthony Wright MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [linux-lvm] Using LVM snapshots for hourly backups Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-lvm@redhat.com I'm trying to work out if there's a way to use LVM snapshots to create hourly backups of my data. I realise that this doesn't protect me against disk/machine failure, but it would really handy in cases where I want easy access to historical files, e.g where I accidentally change/delete a file or I want to compare historical files/directories to the current versions to see what's been changed. I thought a really simple and ingeneous approach would be to use LVM snapshots so that each hour I make a snapshot, and remove the snapshot from 24 hours ago, thus having a rolling hourly backup. However when I tried this I ended up with 24 snapshots of the original volume which means a single change to the original volume causes each snapshot to do a Copy on Write of the changed block, so if I change one block on the original volume the snapshots create 24 copies of the original volume which isn't very good for disk performance or disk usage!! What I'd really want is to daisy-chain the snapshots so that snapshot-3hours is a snapshot of snapshot-2hours, which is a snapshot of snapshot-1hour, which is a snapshot of the original volume, thus if a block in the original volume changes only snapshot-1hour is changed and once a snapshot is older than an hour it cannot change any more. I notice that you can't make snapshots of snapshots, so I suspect what I'm looking for isn't possible, but I thought I check and if it isn't possible suggest it as a really useful feature for the future. Your thoughts/comments would be welcome. Thanks, Tony Wright.