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Re: [Xen-users] Backup DomU volumes

To: Marc Patino Gómez <mpatino@xxxxxxxxxxxx>
Subject: Re: [Xen-users] Backup DomU volumes
From: Pavel Georgiev <pavel@xxxxxxxxxxxx>
Date: Tue, 2 Oct 2007 18:11:59 +0300
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Sounds about right, except that it will probably take too much time to make 
snapshots of 270GB volumes. How long would that take and how much space would 
it require.

On Tuesday 02 October 2007 16:57:26 Marc Patino Gómez wrote:
> Hi Pavel,
> In my opinion, using LVM will help you. When you want  backup a running
> VM which his VBD is on a LVM volume you can make a snapshot, then mount
> the snapshot, after this, make the rsync and finally remove the snapshot.
> Best regards,
> Marc
> Pavel Georgiev wrote:
> > Hi List,
> >
> > I`m trying backup the volumes of VMs running on a xen server (3.1). I`ll
> > backup ext3 and reiserfs volumes. My goal is to backup them from Dom0 so
> > that I can avoid messing with DomU (adding scripts, cronjobs etc.). I
> > have another server running xen and I plan to keep exactly the same
> > volumes on it so I can start the VMs on this server in case my main
> > server dies.
> >
> > The way I see it, I`ll be mounting volumes on both servers and
> > doing 'rsync -avP' on the content (in order to avoid transferring already
> > existing file). The problem (maybe not a problem of xen, but I guess
> > other people have bumped into this) is how do I mount volumes without
> > stopping the VMs and without corrupting the data on the volumes.
> >
> > When a volume is in use by a VM, it either has the "need_recovery" flag
> > (ext3) or cannot be mounted ro (reiserfs). I could remove the
> > "need_recovery" flag for ext3 volumes and mount them read-only, do the
> > sync and then umount and set the flag again. For reiserfs I could mount
> > the volume read-write, remount read-only and then do the sync. Are those
> > two approaches safe? Is this going to corrupt my volumes, after all I`ll
> > do some writing (removing the flag for ext3 and replaying the journal for
> > reiserfs)?
> >
> > In general, what are my options if I want to copy the volumes to another
> > server (hopefully only the changed files) without stopping the VM. The
> > rsync does not have to be atomic, it is OK if DomU writes some data after
> > I start rsync.
> >
> > _______________________________________________
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