Ok. Cool. Thanks very much for the knowledge. I have so much more to learn about LVM. So, by quiesce, would you suggest then, that I stop samba, nfs, apache - take a snapshot and immediately restart them? Then, fire off my backups? Stopping/starting nfs can really wreak havoc on connections (e.g. 'stale file handles' and all). For my clarification, and possibly others as well, what happens if, during a snapshot, someone is writing a file to the server via nfs? Is this file snapshotted is an unstable state? Is it skipped? Should I issue a sync immediately prior to snapshotting? How does snapshotting handle this case? Regards and thanks, -- Christopher Barry Manager of Information Systems InfiniCon Systems http://www.infiniconsys.com -----Original Message----- From: Alasdair G Kergon [mailto:agk@uk.sistina.com] Sent: Friday, March 21, 2003 10:25 AM To: linux-lvm@sistina.com Subject: Re: [linux-lvm] LVM snap size weirdness... You're quite right - you must *always* worry about applications changing the filesystem when taking a backup. Backing up from a filesystem snapshot means your backup will at least contain the complete filesystem as it looked at the moment in time when the snapshot was created. (Consider instead if you were to run 'tar' on a changing filesystem: if a process was moving directories at the same time, your tar backup might completely miss them e.g. if they were moved from a place 'tar' hadn't backed up yet into a place it already had. If you backup from a snapshot, that problem disappears.) If you backup from a snapshot, you want to ensure that your on-disk application data is consistent (i.e. checkpointed) at the time you create the snapshot. So you have to worry about applications that are running at the point at which you take the snapshot: e.g. quiesce them, take the snapshot, then set them off again. Alasdair -- agk@uk.sistina.com _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
