Redundancy and backup are not the same thing. RAID gets you redundancy but if you get pwnd, you get redundantly pwnd!
So you backup to elsewhere. Now you have two copies of your data. Cool. Now you probably can recover from a silly mistake from up to a week ago or whatever your retention period is. However, if you don't monitor your backups, you'll never notice certain snags such as ransomware. OK, that might be low risk for your home backups.
It's quite hard to get the balance right but I think that you might not be quite as protected as you think you are. Why not buy a cheap hard disk and clone all your data to it every three or six months and stash it somewhere?
I have a similar argument with a colleague of mine, to the point that I will probably buy a LTO multi head unit myself and some tapes.
RAID is not a backup, its a data integrity thing. It ensures that what you save now stays saved correctly into the future. It protects now. Backups protect the past.
Think long and hard about what might go wrong and take suitable steps. For you I think a simple, regular off line back up will work out quite well with minimal cost, for disaster recovery.
I didn’t actually specify it out, but my third backup is an offline SSD that I plug in every once in a while and store at my office. I only mentioned the RAID for local redundancy reasons.
You are right about the data being corrupted, either maliciously or bitrot. The NAS is not accessible outside my home network, so I think I am ok there.
Bitrot would require snapshots and full backups stored over time, which I could do fairly easily but I am currently not.
So you backup to elsewhere. Now you have two copies of your data. Cool. Now you probably can recover from a silly mistake from up to a week ago or whatever your retention period is. However, if you don't monitor your backups, you'll never notice certain snags such as ransomware. OK, that might be low risk for your home backups.
It's quite hard to get the balance right but I think that you might not be quite as protected as you think you are. Why not buy a cheap hard disk and clone all your data to it every three or six months and stash it somewhere?
I have a similar argument with a colleague of mine, to the point that I will probably buy a LTO multi head unit myself and some tapes.
RAID is not a backup, its a data integrity thing. It ensures that what you save now stays saved correctly into the future. It protects now. Backups protect the past.
Think long and hard about what might go wrong and take suitable steps. For you I think a simple, regular off line back up will work out quite well with minimal cost, for disaster recovery.