[ceph-users] activating cache tier while rbd is in use

Hello all, is it allowed to configure and activate a cache tier for a pool that contains used RBD images? The documentation (https://docs.ceph.com/docs/mimic/rados/operations/cache-tiering/) doesn't say anything about this, but we have experienced errors with our VMS consuming ceph rbd volumes. Is there any other preparation measure before we would issue the set-overlay command? Kind regards, Laszlo