You would be backing up anyway if the data is that important. RAID != backup.

I don't see any problem with parity based RAID systems. Okay, if any two drives fail together in a single parity RAID then you're screwed. If you have to guard against 2 drive failure then use double parity. If that still isn't enough then restore from your backup. If your drives are failing quickly enough that you don't have any time to get your hotspare going then you've got bigger issues.

At work we've got several NetApp filers running RAID DP which are replicated to our 2nd site. Even so, we still snapshot and backup regularly.