Ceph » rbd

We want to back up a large number of rbds from cluster A to cluster B, which were cloned from same snap of template.
However，the difference file exported by rbd export/export-diff contains the content of the parent.
If the rbd export/export-diff support exclude parent content, we can reduce a large amount of data transmission,
and in cluster B, shared parent content can also be used to save space.