Re: [Qemu-devel] qcow2 snapshot + resize

[John Snow]

On 01/05/2016 08:55 AM, Eric Blake wrote:
> On 01/05/2016 05:10 AM, lihuiba wrote:
> 
>>>> In our production environment, we need to extend a qcow2 image with
>>>> snapshots in it.
> 
>>> The thing is that one would need to update all the inactive L1 tables. I
>>> don't think it should be too difficult, it's just that apparently so far
>>> nobody ever had the need for this feature.
> 
> Is resizing a snapshot really what you want?  Ideally, a snapshot tracks
> the data from a point in time, including the metadata of the size being
> tracked at that time.  Extending the snapshots then reverting to that
> snapshot means your guest would see a larger disk on revert than it did
> at the time the snapshot was created, which guests might not handle very
> well.
> 

Unless reverting to a snapshot also implied undoing the re-size.