CephFS Snapshots

CephFS snapshots create an immutable view of the file system at the point in time they are taken. CephFS support snapshots which is managed in a special hidden subdirectory named .snap .Snapshots are created using mkdir inside this directory.

Snapshots can be exposed with a different name by changing the following client configurations.

  • snapdirname which is a mount option for kernel clients

  • client_snapdir which is a mount option for ceph-fuse.

Snapshot Creation

CephFS snapshot feature is enabled by default on new file systems. To enable it on existing file systems, use the command below.

$ ceph fs set <fs_name> allow_new_snaps true

When snapshots are enabled, all directories in CephFS will have a special .snap directory. (You may configure a different name with the client snapdir setting if you wish.) To create a CephFS snapshot, create a subdirectory under .snap with a name of your choice. For example, to create a snapshot on directory /file1/, invoke mkdir /file1/.snap/snapshot-name

$ touch file1
$ cd .snap
$ mkdir my_snapshot

Using snapshot to recover data

Snapshots can also be used to recover some deleted files.

  • create a file1 and create snapshot snap1

$ touch /mnt/cephfs/file1
$ cd .snap
$ mkdir snap1

  • create a file2 and create snapshot snap2

$ touch /mnt/cephfs/file2
$ cd .snap
$ mkdir snap2

  • delete file1 and create a new snapshot snap3

$ rm /mnt/cephfs/file1
$ cd .snap
$ mkdir snap3

  • recover file1 using snapshot snap2 using cp command

$ cd .snap
$ cd snap2
$ cp file1 /mnt/cephfs/

Snapshot Deletion

Snapshots are deleted by invoking rmdir on the .snap directory they are rooted in. (Attempts to delete a directory which roots the snapshots will fail; you must delete the snapshots first.)

$ cd .snap
$ rmdir my_snapshot