I think it’s great you brought up RAID but I believe when Immich or any software mess things up it’s not recoverable right?
RAID is not a backup, no. It’s redundancy. It’ll keep your service up and running in the case of a disk failure and allow you to swap in a new disk with no data loss. I don’t know how Immich works but I would put it in a container and drop a snapshot anytime I were to update it so if it breaks I can just revert.
I’m sure there’s ways to do it, but I can’t do it and it’s not something I’m keen to learn given that I’ve already kind of solved the problem :p