Re: [Xen-devel] Does XEN have any hot backup/snapshot features or plan?

[Dutch Meyer <dmeyer@xxxxxxxxx>]

Hot snapshot capabilities are in blktap2 (in xen-unstable) for qcow and 
vhd.  However, there's no unified snapshot interface.  Each driver has its 
own interface, but you could script something up for one or more disk 
types pretty easily. Check out tools/blktap2/vhd/vhd-util.
--Dutch

On Sun, 14 Jun 2009, Omar BENHAMID wrote:

> Hi,
> I was thinking of prototyping "hot snapshotting" of blktap backed vbds.
> The idea would be for example : for a domain called MyDomain having
> /var/xen/data/mydisk.vmdk attached to hda
>
> xm vbd-snapshot-create MyDomain hda /var/xen/snapshot/snapshot1.vmdk
>
> xend will then synchronise the domain, pause it and signal blktap daemon to
> create a disk snapshot : Current block device attached to hda would be
> closed and moved to /var/backup/snapshot1.vmdk than recreate mydisk.vmdk as
> a cow copy of snapshot1.vmdk then unpause the domain. snapshot1.vmdk could
> be backed up safely as it receives no writes. After backup imagine some
> thing like :
>
> xm vbd-snapshot-merge MyDomain hda
>
> That would "commit" mydisk.vmdk into snapshot1.vmdk, either with a paused
> domain or (more complex but more confortable) live.
>
> - How interesting this would be for general use ? Interface should of course
> be generic enought to support large variety of tap storage backends (cow,
> vmdk, vhd ?). Would it be interesting enought to some day get integrated in
> mainstream xen ? Or philosophy of lean means that we won't implement in xen
> something that LVM would do fine ?
>
> - Is there already some work like this ?
>
> - As of xen 3.2 (and hopefully 3.3) i think blktap daemon is the right place
> to do it, adding the right callbacks to tap_disk structure and implementing
> it in convinent drivers. But i saw plans with xen 3.4 (or after ?) with the
> idea of deep rework trying to merge everything in qemu device model? What is
> the best place to do this ?
>
>
>
> Regards,
>
> Omar BENHAMID
>
>
> On Mon, Apr 6, 2009 at 1:47 AM, zign <zign@xxxxxxxxxxxxxxxx> wrote:
>
> > Hello everybody,
> >  My name is Zign and I would like to ask a simple question.
> >  For example, I want to backup my VMs everyday. But I do not
> > want them to be stopped while the backup. For this reason, I can't
> > use a traditional way like:  freeze the VM  -> backup everything ->
> > restore the VM.
> >  So is there any solution for this?
> >
> > --
> > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> > Zhao Yue
> >  Esaki Laboratory,
> >  Information Physics & Communication Engineering,
> >  Graduate School of Information Science and Technology,
> >  The University of Tokyo
> > Email: zign@xxxxxxxxxxxxxxxx
> >       zign@xxxxxxx
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
>
>
> --
> Omar BENHAMID
> Email: o.benhamid@xxxxxxxxx
> Tel: +33 6 09 31 60 60
> http://www.bewigo.fr
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