Q: I need an example of when RAID 1 with multiple drives is used. I can't find a single reference to it being implemented anywhere.

A: RAID 1, by definition, requires at least two disk drives. Storage system vendors and even application vendors like Oracle also support triple mirror RAID. Another implementation of multiple drive RAID 1 would be a hybrid RAID 0+1 or 1+0, which is also known as RAID 10. This implementation works well when, for example, six disk drives are used with three each in the two unique RAID groups that are then striped or mirrored together (this depends on whether you're using 0+1 or 1+0). Another example occurs when vendors implement a combination of horizontal and vertical RAID. One RAID group is created horizontally across a group or shelf of disk drives and another RAID group, using perhaps a different RAID level, is created vertically.

--Greg Schulz, founder and senior analyst StorageIO Group