[sheepdog-users] how about the data relastionship with snapshot and clone

[Liu Yuan]

On Tue, Dec 31, 2013 at 06:24:13PM +0800, redtone wrote:
> OS Provision with snapshot and clone
> 
> 1, dog vdi create windows2003
> 2, install windows 2003 on the vdi disk
> 3, dog vdi snapshot -s osbase windows2003
> 4, dog vdi clone -s osbase windows2003 kvm01_os
> 5, running VM on kvm01_os 
> 6, dog vdi delete -s osbase windows2003
> 
> I wander if the the VM on kvm01_os will crashed because I delete the
> snapshot osbase, because the kvm01_os is cloned from the osbase snapshot.
> 
> In fact the VM on kvm01_os will not crash when I delete the snapshot osbase.
> I am not sure about this. I think this is not safe. Anyone can clear it?

Currently, we make a very simple reference count on the objects in the
snapshot/clone chain, that is: don't delete objects if there is any outstanding
reference.

So in your case, you just delete the base image but not its data because its
data are referenced by other vdis.

Thanks
Yuan