Re: [Xen-users] Backups !

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

At 16:16 -0500 30/7/09, Paras pradhan wrote:
> My Virtual machines resides on a GFS partition folder (e.g: /guests) .
> I can not take LVM snapshot because CLVM is not yet supported for
> snapshot. DD takes ages to create backups. What is the traditional
> method to backup virtual machines.
>
> does rdiff-backup make sense in my case?
I treat each VM as though it was a standalone device - and do the 
backup from inside it. Without a lot of effort you CANNOT make a 
clean, consistent, and practical backup of a VM from 'outside'. If 
you snapshot the underlying storage then you will have incomplete 
image of the filesystem as you will NOT capture any cached pending 
writes - a good journalling filesystem will reduce, but not 
eliminate, the problem. To get a consistent and current image of the 
filesystem would require you to freeze the VM and copy it's state 
alongside the storage image - but then the only way to restore would 
mean restoring the entire VM to the exact running state at that point 
in time. And of course, if you have any applications (particularly 
database type) then they will typically have their own caching as 
well.
The two tools I use are rsync and rdiff-backup

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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