What do you guys think? I am not good at math, especially possibility calculation. Here is what I am wondering.

Is RAID operation (any level) inherently less stable/reliable than operating independent disks?

If the above is true, then wouldn't it be better to make 2 sets of backup on 2 independent disks? 1) You end up using the same number of disks anyway 2) In a RAID 1 array, when one of the independent disks fails, you are under the pressure to replace it immediately. On the other hand, in the case of 2 independent disks, you'll have immediate access to the backup on the remaining disk.