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

To: zign <zign@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Does XEN have any hot backup/snapshot features or plan?
From: Brendan Cully <brendan@xxxxxxxxx>
Date: Sun, 5 Apr 2009 16:54:50 -0700
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On Monday, 06 April 2009 at 08:47, zign 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?

I don't know of a complete tool, but the parts are all there. xm save
-c creates a checkpoint of a VM without destroying it, and LVM lets
you easily snapshot a disk. You can tie them together using the
external device migration hook in xend -- I think I posted a demo
script to this list many months ago that does this.

I can't remember whether xm save -c also supports --live in xend, but
if not it's a trivial change that can reduce the time that the VM is
paused for backup to almost nothing. The checkpoints may be larger in
that case, but they can be folded down to simple images afterwards. I
have a script somewhere around here that does this rewriting, but I
haven't used it in some time.

You might also think about running your VM on parallax, and saving its
images there too -- parallax can figure out the deltas between series
of images for you automatically.

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