Selfhosted

If you know Linux, I recommend going with some form of software raid. A lot of people might recommend ZFS but I would recommend btrfs with Linux. Using btrfs you can add and removed drives of any size at will unlike ZFS. That and with btrfs you don’t need to worry about vdevs and stuff. Simple, easy to use, and simple to upgrade. Just use btrfs, set data to raid1 and metadata to raid1c3 and you will have a rock solid system. That and you won’t have to worry about dkms or kernel changes breaking your data storage. Also before someone mentions it there was a btrfs raid5 write hole but that was fixed in Kernel 6.2

Another future interesting option might be btreefs. Just got merged into kernel mainline and has amazing features.

ZFS zRAID is pretty good for this I think. You hook up the drives from one "pool" to a new machine, and ZFS can detect them and see that they constitute a pool and import them.

I think it still stores some internal references to which drives are in the pool, but if you add the drives from the by-ID directory when making the pool it ought to be using stable IDs at least across Linux machines.

There's also always Git Annex for managing redundancy at the file level instead of inside the filesystem.