Dear Ceph community, We want to restructure (i.e. move around) a lot of data (hundreds of terabyte) in our CephFS. And now I was wondering what happens within snapshots when I move data around within a snapshotted folder. I.e. do I need to account for a lot increased storage usage due to older snapshots differing from the new restructured state? In the end it is just metadata changes. Are the snapshots aware of this? Consider the following examples. Copying data: Let's say I have a folder /test, with a file XYZ in sub-folder /test/sub1 and an empty sub-folder /test/sub2. I create snapshot snapA in /test/.snap, copy XYZ to sub-folder /test/sub2, delete it from /test/sub1 and create another snapshot snapB. I would have two snapshots each with distinct copies of XYZ, hence using double the space in the FS: /test/.snap/snapA/sub1/XYZ <-- copy 1 /test/.snap/snapA/sub2/ /test/.snap/snapB/sub1/ /test/.snap/snapB/sub2/XYZ <-- copy 2 Moving data: Let's assume the same structure. But now after creating snapshot snapA, I move XYZ to sub-folder /test/sub2 and then create the other snapshot snapB. The directory tree will look the same. But how is this treated internally? Once I move the data, will there be an actually copy created in snapA to represent the old state? Or will this remain the same data (like a link to the inode or so)? And hence not double the storage used for that file. I couldn't find (or understand) anything related to this in the docs. The closest seems to be the hard-link section here: https://docs.ceph.com/en/quincy/dev/cephfs-snapshots/#hard-links Which unfortunately goes a bit over my head. So I'm not sure if this answers my question. Thank you all for your help. Appreciate it. Best Wishes, Mathias Kuhring _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
 |