Yeah, that wasn’t meant to be remotely comprehensive: there’s a lot of ways you can do this ranging from the filesystem to what kind of archives you’re storing, to programs that make parity data for validation.

…also, since I haven’t started a flamewar yet today, I don’t think I’d personally use BTRFS. It’s still too new, has had data consistency issues too recently, and just plain doesn’t have the kind of historical performance record for something I’d want to use for archival purposes.

Come back in another decade and we’ll see how it’s been going.