Ceph » rbd

it should be a feature instead of bug.

Jason Dillaman wrote:

@yang guo guo: can you provide more background on your intended request use-case? If you are trying to implement a secure deletion, I think the only way to solve that would be directly on the OSDs upon truncate/remove operations. The rationale is that if an image has a snapshot, the removal of the backing copy-on-write objects is handled 100% by the OSDs and librbd would have no mechanism to overwrite the read-only snapshot data.

Yes, I mean the secure deletion. about the snapshots, what about iterating the all snapshots of an image and overwrite each of them by zero/random-data. Then we will delete the HEAD of this image. That means we overwrite the all copies of it even it is cow-ed in snapshots.

@yang guo guo: As I mentioned, there is no way for librbd to overwrite snapshot objects -- they are read-only from the point-of-view of librbd/librados users. Therefore, the only way this could be implemented would be directly within the OSDs as a global configurable option.

Okey, makes sense. will investigate more about it in osd. thanx

Jason Dillaman wrote:

@yang guo guo: As I mentioned, there is no way for librbd to overwrite snapshot objects -- they are read-only from the point-of-view of librbd/librados users. Therefore, the only way this could be implemented would be directly within the OSDs as a global configurable option.