The rbd diff-related commands compare points in time of a single image. Since children are identical to their parent when they're cloned, if I created a snapshot right after it was cloned, I could export the diff between the used child and the parent. Something like: rbd clone child parent at snap rbd snap create child at base <use child image> rbd snap create child at changed rbd export-diff child at changed --from-snap base child_changes.diff the questions are: 1. Does the child at base really necessary? It seems point the same obj with parent at snap, why should'n I use the parent at snap instead? 2. If I create child at base, comparing with use child image directly, are there some performance redundant or storage increment when writing the child image later? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.ceph.com/pipermail/ceph-users-ceph.com/attachments/20140821/99288bcc/attachment.htm>
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