[sheepdog-users] Start a guest from a snapshot

[MORITA Kazutaka]

At Thu, 21 Mar 2013 18:06:37 +0800,
Liu Yuan wrote:
> 
> On 03/21/2013 05:54 PM, Valerio Pachera wrote:
> > 2013/3/21 Liu Yuan <namei.unix at gmail.com>:
> >> QEMU client will actually clone the specified snapshot and start the
> >> clone which copy-on-write the specified snapshot.
> > 
> > That means the vdi with id =  0 will never be affected by changes on
> > the snapshot.
> > Is that right?
> > 
> 
> Yes. id = 0 means it is not the snapshot and isn't affected.
> 
> Well, from the 'collie vdi list', it seems that the internally created
> VDI is also snapshot. It looks weird to me, because this new VDI is
> writeable(I am not sure of it, but I can do 'dd' inside). So it is

If we start from a snapshot, a new writable vdi will be created as its
child.  The previous writable vdi will be kept as a snapshot because
we allows only one writable vdi for each vdi name.  If you want to
keep two writable vdi, you have to create a different vdi name (I
think this restriction is same as VMware or VirtualBox).

> better seen as a clone. Kazutaka, is this intentional? How about marking
> this VDI as clone?

IIUC, we mark a vdi as clone only when it is cloned from the other vdi
name.  However, to be honest, I don't understand the intention of 'c'
mark in the vdi list.  It's you who merge the patch to introduce the
mark, so if you think we should mark the vdi as clone, I'm not against
it.

Thanks,

Kazutaka