How to upgrade PBS to Debian Trixie for ZFS 2.3+ vdev expansion?

[pulipulichen]

Hi everyone, I'm currently managing a Proxmox Backup Server (PBS) instance that's running out of storage space in the datastore.

My current environment is PBS based on Debian Bookworm, which uses ZFS 2.2.6. As many of you know, older ZFS versions do not support adding a single drive to an existing RAID-Z vdev for expansion; typically, you'd have to rebuild the pool.

However, ZFS 2.3 finally supports "RAID-Z Expansion," allowing us to attach new disks directly to an existing vdev. To use this, I plan to upgrade PBS to the Debian Trixie path to get the latest ZFS modules. I've drafted a workflow and would appreciate your feedback on any potential risks:

1. Update Bookworm to the latest and set Datastore to maintenance mode:

apt update && apt dist-upgrade
proxmox-backup-manager datastore update <name> --maintenance-mode read-only
pbs3to4 --full
reboot

2. Modify source lists to Trixie and perform a dist-upgrade:

sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/pbs-enterprise.list
apt modernize-sources && apt update && apt dist-upgrade

3. Perform zpool upgrade and then zpool attach for the expansion:

zpool upgrade <pool-name>
zpool attach <pool-name> <vdev-name> /dev/disk/by-id/<new-id>

Are there any pitfalls in this process? Specifically, should I be worried about the bootloader warnings during the pbs3to4 check?