"CephFS supports asynchronous replication of snapshots to a remote CephFS file system via cephfs-mirror tool. Snapshots are synchronized by mirroring snapshot data followed by creating a snapshot with the same name (for a given directory on the remote file system) as the snapshot being synchronized." ( https://docs.ceph.com/en/latest/dev/cephfs-mirroring/ )

We found ZFS led to maintenance issues, but it was probably unrelated to the filesystem per say. i.e. culling a rack storage node is easier than fiddling with degraded raids.