Well, it’s IT, so the answer is always a big ol’ fat, “It depends!”

Why do we do this?

Ostensibly, the primary reason for RAID is in the name: redundancy. Of course, there’s RAID 0, which is for performance, but that’s kind of a different thing that doesn’t seem to apply here. The main risks it mitigates are those associated with drive failures.

RAID isn’t, and should’t be considered, a substitute for backups. But, backups can be a substitute for RAID in some situations. If you simply want to avoid losing data, the right backups solution can do that for you, but your time to recovery will be longer; rebuilding a RAID disk from parity is much faster than restoring a backup from scratch.

So, if you want, you can RAID some disks, partition space on those disks and store your important data on the RAIDed partition. The rest can live on backed up but un-RAIDed disks. It’s really according to your specifically desired recovery time and risk appetite for that data.