Is it possible to join an external Ceph Hammer with pve 6

[chrwa]

We have an old PVE-Cluster 4.4 with an external Ceph Hammer. I want join the old Ceph cluster from the new PVE 6.1 with internal Ceph for to copy the VM's from old to new.
Joining the Ceph Hammer everything looks fine, until I want to see the content. Trying to do this I get the message "rbd error: rbd: listing images failed: (95) Operation not supported (500) ".
I wonder if the combination is supported at all.

 

[Alwin]

AFAIK, no. Usually it only works with one version in between. A Luminous Client could access a Jewel and Nautilus cluster. Hammer might be just to far off.
https://ceph.io/community/new-luminous-upgrade-complete/