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Re: [Xen-users] Backup; mount domU FS RO?

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Backup; mount domU FS RO?
From: Andy Smith <andy@xxxxxxxxxxxxxx>
Date: Mon, 19 Dec 2005 12:22:38 +0000
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On Mon, Dec 19, 2005 at 08:04:50AM +0100, als@xxxxxxxxxxxxxxx wrote:
> A better approach is to use LVM and snapshots. Use LVM logical volumes
> as "disks" for your DomU (if you aren't already doing this), create
> snapshots for your backups, mount the snapshots and backup _those_.
> After the backup, umount the snapshots and destroy them.
> Don't forget to allocate enough storage to your snapshots to cover any
> changes in the volume.
> I'm currently using this to backup our production DomU systems from the
> Dom0 and it works very well.

So was I, but as the number of snapshots increased my LVM devices
began to experience deadlocks leading to the whole machine having to
be reported.

When reported to Red Hat the word is that LVM snapshots are not yet
ready for heavy production use.  This is after discounting lack of
memory in dom0 or too-small snapshot LVs.

If you look in the archives of the LVM list you will see multiple
people reporting the same issues, it is not peculiar to Xen.

I am eagerly awaiting the time when I can start doing this again,
but until then I prefer my block devices to work.


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