Re: [Xen-users] iSCSI Volumes and Xen

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Jan 14, 2010 at 03:28:29PM -0000, Matthew Law wrote:
> On Thu, January 14, 2010 2:22 pm, John Madden wrote:
> > Keep in mind that snapshots are not backups.  There's no way that
> > snapshot would be consistent unless you were also doing something on the
> > domU to stop and flush all i/o and clear the scsi caches.
> 
> Understood.  Does suspending the domU do the job?  I wanted to:
> 
> - 'xm save' the domU
> - snapshot the domU's zvol on the storage server
> - 'xm restore' the domU
> 
> this will give me a consistent snapshot, right?  
>

No, I don't think this will give you consistent disk snapshot.

Before "xm save" you need to to make sure all the applications
(databases etc) are shut down, they have flushed their buffers/caches,
the filesystem and kernel have flushed their caches, and THEN you can
save the the domU, or take the snapshot directly.

-- Pasi

> I know this means the domU will be unavailable for the duration of the 
> snapshot.  
> In my experience zfs snapshots are very quick indeed - much quicker than lvm.
> 
> Is the only backup option for a running domU to run a conventional backup
> client within it, such as bacula?
> 
> Thanks,
> 
> Matt.
> 
> 
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