From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m3MAVRNu006313 for ; Tue, 22 Apr 2008 06:31:27 -0400 Received: from smtp03.atlngahp.sys.nuvox.net (smtp-out3.atlngahp.sys.nuvox.net [70.43.63.20]) by mx3.redhat.com (8.13.8/8.13.8) with ESMTP id m3MAUv5V008373 for ; Tue, 22 Apr 2008 06:30:58 -0400 Received: from smtp.media-brokers.com (70.43.81.99.nw.nuvox.net [70.43.81.99]) by smtp03.atlngahp.sys.nuvox.net (8.13.1/8.13.1) with ESMTP id m3MAUjsD028524 for ; Tue, 22 Apr 2008 06:30:45 -0400 Received: from [192.168.1.110] (sjester.atl.media-brokers.com [192.168.1.110]) by smtp.media-brokers.com (Postfix) with ESMTPSA id E98B52A57D5 for ; Tue, 22 Apr 2008 06:30:44 -0400 (EDT) Message-ID: <480DBE54.1090406@Media-Brokers.com> Date: Tue, 22 Apr 2008 06:30:44 -0400 From: Charles Marcus MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [linux-lvm] Snapshot question... 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 Ok, now I have a question on how snapshots work... I've read the following links: http://tldp.org/HOWTO/LVM-HOWTO/snapshotintro.html http://tldp.org/HOWTO/LVM-HOWTO/snapshots_backup.html but am still unsure of something... When a snapshot volume is created, it only needs to be large enough to accommodate any *changes* to the volume I'll be taking a snapshot of, correct? So, on a low volume mail server, 5GB should be way more than enough, especially if done in the middle of the night when it is essentially idling, right? I'm guessing that 500MB would probably be more than enough, but disk space is cheap, and I have plenty. So, I have allocated 5GB of 'free space' in my volume group for snapshot use. What I don't understand is... why am I mounting and then backing up the newly created snapshot volume, if it only contains the *changes* to the volume I really want to backup - which in my case is /var/virtual? If the snapshot volume is only 5GB, how, by backing up *this* volume, am I backing up over 100GB of data that is in a different volume? Tia for any responses, -- Best regards, Charles