[Sheepdog] [PATCH] sheep: use hash value for vdi attribute object id

[MORITA Kazutaka]

At Wed, 3 Aug 2011 12:04:29 +0100,
Chris Webb wrote:
> 
> MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp> writes:
> 
> > Thank you for your testing.  I've implemented another approach.
> > Could you try again?
> 
> Hi Kazutaka. Yes, this one works fine, and survives the deletion of
> snapshots nicely.

Thanks!  I've pushed the patch to the main git repository.

> 
> > The vdi id can change if we get the snapshot, so there is a problem
> > that vdi attributes vanish after taking snapshots.  This patch uses
> > the hash value for the vdi attribute object id instead of the vdi id.
> 
> Am I right in thinking that implementing in this way precludes the future
> implementation of vdi rename, or do existing assumptions in the design
> already make this impossible?

Sheepdog also uses a hash value of the vdi name to look up vdi
objects, so it is already difficult to implement vdi rename simply,
but I think it is not impossible.  For example, if we log all the vdi
rename operations, we can traverse the renamed vdi name and get the
correct hash value based on the old vdi name.


Thanks,

Kazutaka