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> There is a restful api[1] to revert volume to snapshot. But the description means
> we can only use this api to revert volume to its latest snapshot.
>
>
> Are some drivers limited to rolling back only to the latest snapshot? Or just nobody
> helps to improve the api to revert volume to any snapshots of the volume?
>

This is partly due to the rollback abilities of each type of storage. Some
types can't revert to several snapshots back without losing the more recent
snapshots. This means that Cinder would still think there are snapshots
available, but those snapshots would no longer be present on the storage
device.

This is considered a data loss condition, so we need to protect against that
from happening. It's been discussed several times at Design Summits and PTGs,
and at least so far there has not been a good way to handle it.

The best recommendation we can give is for anyone that needs to go back several
snapshots, you will need to revert one snapshot at a time to get back to where
you need to be.

But it is also worth pointing out that snapshots, and the ability to revert to
snapshots, is not necessarily the best mechanism for data protection. If you
need to have the ability to restore a volume back to its earlier state, using
the backup/restore APIs are likely the more appropriate way to go.

Sean