RAID 0 - Provides striping of file bits across other volume(s). At least 2 drives are required; no redundancy is provided (one drive failure results in data loss).
RAID 1 - Mirrors the data from one drive to another. At least 2 drives are required and 1 drive may fail without data loss.
RAID 3 & 4 - Provides striping across multiple volumes and a dedicated volume for parity bits. It basically combines the functions of RAIDs 0 and 1. At least 3 drives are required and one drive may fail without data loss.
RAID 5 - Striping across multiple volumes with parity bits. At least 3 drives are required and 1 drive may fail without data loss.
RAID 6 - Same as RAID 5 except that at least 4 drives are required and up to 2 drives are permitted to fail and break the array without data loss.