I hate trying to remember which version of RAID does what. Maybe this will help:
|0 Zero||Speed, still fails.|
|1 One||1:1 redundant, faster read, slow writes|
|5 Five||Stripe with parity, fast, more reliable|
|6 Six||Like 5, but takes more disks.|
|10 Ten or "One plus Zero"||Striping and mirroring. Speed and reliable. $$$|
|01 or Zero plus One||Same as 10 (as far as you care)|
Of course, if Drobo has their way none of this will matter within a few years because we'll all be using their solutions (or something like it).