Hi,
We have update ceph to v20 in production using ganeti(qemu) in debian12, rbd(with EC) and cephfs without any problem/downtime.
The only thing is that we can't set allow_ec_optimizations until 20.2.1 released or bugs fixed.

Other problem is with set-require-min-compat-client we have to maintain it on luminous due to kernel doesn't suport mount cephfs with higher client version.

In virtualization nodes we use ganeti (it uses qemu) and we have also update librbd to v20.

Version we are using:
* ceph 20.2.0
* qemu 7.2
* librbd 20.2.0
* libvirt 9.0

Maybe you can check libvirt/librbd versions and check "ceph features".
This is our "ceph features":

$ ceph features
{
   "mon": [
       {
           "features": "0x3f07fffffffdffff",
           "release": "squid",
           "num": 5
       }
   ],
   "mds": [
       {
           "features": "0x3f07fffffffdffff",
           "release": "squid",
           "num": 4
       }
   ],
   "osd": [
       {
           "features": "0x3f07fffffffdffff",
           "release": "squid",
           "num": 120
       }
   ],
   "client": [
       {
           "features": "0x2f018fb87aa4aafe",
           "release": "luminous",
           "num": 8
       },
       {
           "features": "0x3f07fffffffdffff",
           "release": "squid",
           "num": 115
       }
   ],
   "mgr": [
       {
           "features": "0x3f07fffffffdffff",
           "release": "squid",
           "num": 3
       }
   ]
}

Best regards,
Alfonso Escribano

Eugen Block via ceph-users wrote:

Hi,

your question is a bit "thin", I'd say. A lot has changed in Tentacle [0],
but nothing of the mentioned changes looks critical wrt libvirt from my
perspective. Do you have any logs or more detailed descriptions what
exactly fails? We haven't upgraded to v20 yet, at least not our prod
cluster, we also use RBD heavily (OpenStack on Ubuntu), so this is quite
relevant for us.

Thanks,
Eugen

[0] https://ceph.io/en/news/blog/2025/v20-2-0-tentacle-released/#rbd

Am Di., 10. Feb. 2026 um 00:06 Uhr schrieb Piotr Pisz via ceph-users <
ceph-users@ceph.io>:

Hello,



We upgraded Ceph to Tentacle, and everything went fine, but all hosts
running Ubuntu 22 and 24 lost connectivity to RBD at the libvirt level.

What has changed in the tentacle?



Best regards,

Piotr





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