Hello, Thanks Ramana for your insightful answer, that's very helpful! The last thing I'd like to ask just out of curiosity -- since there's at most only one <UUID> dir in /volumes/<subvol group>/<subvol>, do you know any details as to why is it a UUID instead of some stable dir name? The reason I ask is I'd like to construct (programatically) an absolute path to a subvolume snapshot, which would be as follows: * /volumes/<subvol group>/<subvol>/.snap/<snap>/<UUID>, or the "old way" that implies the subvolume still exists * /volumes/<subvol group>/<subvol>/<UUID>/.snap/_<snap>_<snap inode number> In both cases this would require directory traversal to find out what this UUID is. Cheers, Robert st 23. 3. 2022 o 4:03 Ramana Venkatesh Raja <rraja@xxxxxxxxxx> napísal(a): > On Tue, Mar 22, 2022 at 11:24 AM Robert Vasek <rvasek01@xxxxxxxxx> wrote: > > > > Hello, > > > > I have a question about cephfs subvolume paths. The path to a subvol > seems > > to be in the format of <subvol group>/<subvol>/<some UUID>, e.g.: > > > > > /volumes/csi/csi-vol-59c3cb5a-a9ee-11ec-b412-0242ac110004/b2b5a0b3-e02b-4f93-a3f5-fdcef80ebbea > > > > I'm wondering about the <some UUID> segment. Where is it coming from, why > > is there this indirection? > > It is the directory within the subvolume where the user's subvolume > data is stored. When you fetch the mount path of the subvolume using > `ceph fs subvolume getpath` command, you get the absolute path of the > directory of the form, /volumes/<subvol gp name>/<subvol name>/<uuid>/ > The indirection was introduced to allow storing subvolume's internal > metadata within /volumes/<subvol gp name>/<subvol name>/, and to > support features such as removing a subvolume while retaining its > snapshots. For more details you can see, > > > https://github.com/ceph/ceph/blob/v16.2.7/src/pybind/mgr/volumes/fs/operations/versions/subvolume_v1.py#L33 > > https://github.com/ceph/ceph/blob/v16.2.7/src/pybind/mgr/volumes/fs/operations/versions/subvolume_v2.py#L22 > > The UUID component of a subvolume's mount path is generated here, > > https://github.com/ceph/ceph/blob/v16.2.7/src/pybind/mgr/volumes/fs/operations/versions/subvolume_v2.py#L168 > > > I suppose this means there can be multiple of > > these UUIDs? > > No. There is only one such UUID directory that stores the user's > subvolume data during the lifecycle of the subvolume. > > > Nowhere in "ceph fs subvolume{,group}" can I find anything to > > list them (without actually traversing <subvol group>/<subvol>/*) > however. > > Or can you give me hints where to look for this in the code? > > `ceph fs subvolume ls` is used to list the subvolume names within a > subvolume group, and `ceph fs subvolume getpath` or `ceph fs subvolume > info` is used to fetch the mount path of a subvolume. There is no > single command to list the mount paths of all the subvolumes within a > subvolume group . Looking at > > https://github.com/ceph/ceph/blob/v16.2.7/src/pybind/mgr/volumes/fs/volume.py#L368 > and > https://github.com/ceph/ceph/blob/v16.2.7/src/pybind/mgr/volumes/fs/volume.py#L329 > should provide clues on how it can be implemented. > > > > > Thank you! > > > > Cheers, > > Robert > > _______________________________________________ > > ceph-users mailing list -- ceph-users@xxxxxxx > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > > > > Regards, > Ramana > > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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