Lutz Vieweg <lvml <at> 5t9.de> writes:

> 
> On 06/30/2015 11:10 AM, David Weber wrote:
> > I use Btrfs with regular snapshots on my workstation with Virtualbox 
since
> > years. Running filefrag on the image doesn't complete after hours but the
> > IO of the VM is still "fast enough". But the definition of "fast enough"
> > can vary heavily.
> 
> How do you backup the VM images? If filefrag takes hours to complete,
> I'd assume that attempting a sequential read of the whole file (from a
> backup software) takes just as long.

I use send/receive. With an SSD it doesn't take that long.

> 
> > If it becomes to slow I will try a btrfs fi deframent or just recreate 
the
> > image with a no reflink copy.
> 
> Chances are this will also take hours.

A sequential read (dd if=Windows7.vdi of=/dev/zero bs=1M) gives nearly raw 
SSD Speed. But CPU consumption is indeed quite high...
> 
> Regards,
> 
> Lutz Vieweg


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