Adding a Second SSD to Proxmox and Configuring ZFS RAID1 Without Data Loss

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WohnZimmerKind

New Member
May 9, 2025
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Hi everyone,

I'm currently running Proxmox VE on a 250GB SSD. The system is up and running fine, but now I want to add a second 250GB SSD and configure ZFS in RAID1 (mirror) for redundancy.

However, I want to avoid touching the existing SSD or reinstalling Proxmox. Ideally, I'd like the second SSD to become part of a mirrored setup, without affecting the current system disk.


My questions are:
  1. Is it possible to add the second SSD and create a ZFS mirror without reinstalling Proxmox or wiping my existing drive?
  2. If it's not using ZFS, is there any workaround to safely migrate to a ZFS mirror?
Any guidance, especially with commands or experiences doing this, would be greatly appreciated!

Thanks in advance.


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What you want to do is:

o Backup your configs,
o Reinstall to ZFS boot/root on new SSD,
o Restore configs to the new ZFS install, make sure everything works,
o BACKUP AGAIN, then
o wipefs -a the original SSD,
o duplicate the partition scheme, and
o attach it to the ZFS single-disk pool as a mirror.

https://pve.proxmox.com/wiki/ZFS_on_Linux

https://pve.proxmox.com/pve-docs/pve-admin-guide.html#chapter_zfs
^ Start at 3.9.5 and read through it, print it out if you have to for reference

https://github.com/kneutron/ansitest/tree/master/proxmox

Look into the bkpcrit script, point it to external disk / NAS, run it nightly in cron.

THIS IS NOT AN EXERCISE FOR THE INEXPERIENCED ADMIN.
THIS IS ADVANCED-LEVEL SYSADMIN STUFF.

DO ***NOT*** TRY THIS FOR THE 1ST TIME ON YOUR MAIN SYSTEM,
AS THERE IS A NON-ZERO CHANCE YOU WILL KNOCK IT INTO A COCKED HAT ON THE FIRST ATTEMPT
AND HAVE TO RESTORE FROM SNAPSHOT FOR A DO-OVER.

EXPERIMENT WITH DOING THIS PROCEDURE IN A VM 1ST!!!!

MAKE SURE ALL YOUR LXC/VMs ARE BACKED UP!!

  1. Is it possible to add the second SSD and create a ZFS mirror without reinstalling Proxmox or wiping my existing drive?
    1. Yes, IF you installed to ZFS in the 1st place. Then you simply replicate the partition scheme, attach )NOT ADD!( the mirror partition and use proxmox-boot-tool to sync the EFI partitions so you can boot from either disk.
  2. If it's not using ZFS, is there any workaround to safely migrate to a ZFS mirror?
    1. Yes, but not the way you think. Standard install uses LVM+ext4. Completely different paradigm.
    2. You would need to backup, reinstall to ZFS on the new disk and restore/recreate essential config files as described above. Then replicate partition layout and attach mirror to the new disk+partition and run the boot tool as described.
https://github.com/kneutron/ansitest/blob/master/proxmox/proxmox-clone-zfs-bootroot-to-mirror.sh

READ the script first, you will have to edit it before running.

I TAKE NO RESPONSIBILITY FOR DATA LOSS. YOU HAVE BEEN WARNED.
 
You could do it, but its a long drawn out process in cli. Probably in rescue system as well. Better to backup and reinstall.
 
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