On 6 October 2026, Rook 1.21.0 made the msgrv2 protocol mandatory by default for Ceph, which requires a Linux kernel of 5.11 or newer. Check your node kernel versions before upgrading, or explicitly disable msgrv2 in the CephCluster resource.

The Proxmox VE 8 branch, released in June 2023 on Debian 12, reaches end of life in August 2026: hypervisor patches stop even though Debian LTS continues. For anyone running Ceph or old containers, the VE 9 upgrade is two separate projects — and a rollback that goes through restore, not reverse migration.