Help for anyone having this boot issue: got this while zfs-initramfs have been installed from debian backports (version 0.8.6-1~bpo10+1, due to invalid priorities) instead of pve version 2.0.4-pve1
Solved it by doing a rollback to last zfs snapshot of rpool/ROOT/pve-1 (when zfs helps fixing another zfs issue) and installing proper version of zfs-initramfs package
Solved it by doing a rollback to last zfs snapshot of rpool/ROOT/pve-1 (when zfs helps fixing another zfs issue) and installing proper version of zfs-initramfs package