openstack team mailing list archive

[Avishay Traeger <AVISHAY@xxxxxxxxxx>]

Hi all,
I had a few questions about snapshot support in Cinder:
1) a. Why is a snapshot a fundamentally different entity than a volume?
   b. Is it because some back-ends don't support the same set of operations
on snapshots?
   c. Is this what the snapshot-to-volume operation was meant to achieve?
   d. If a back-end supports nested snapshots, each snapshot will need to
be converted to volume before a nested snapshot can be taken?
   e. And in this case, will the back-end driver simply do nothing for the
snapshot-to-volume operation?
2) Why can't you take snapshots of attached volumes?  I think most/all
back-ends will be fine with it (of course they will be crash-consistent if
the OS/application doesn't sync to disk).
3) Most back-ends support various types of snapshots - e.g., read-only,
read-write, full copy, etc.  How can we better support this notion?

Thanks,
Avishay