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

[Omar BENHAMID <o.benhamid@xxxxxxxxxx>]

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

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-- 
Omar BENHAMID
Email: o.benhamid@xxxxxxxxx
Tel: +33 6 09 31 60 60
http://www.bewigo.fr

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