Very nice article, but I found one error (semantics, but an error)
Mean Time Before Failure (MTBF) - you have it as MBTF ...
The MTBF is not altered in any way, regardless of the RAID type implemented. The
Real Time Before Failure may change, as a drive may be under heavier average use than if used as a stand alone drive. The Mean Time is a constant - X hours of actual usage.