RAID 0 stripes data across all hard drives in array; one drive failure takes out all data, no recovery possible. It is only for size; storing data you do not have backed up is a bad idea on this array. RAID 1 mirrors data striped on one drive on a second drive; one drive's failure does not kill data stored on mirror. Redundancy provides minimal data safety. RAID 5 stripes data across 3 drives minimum, up to 15 drives are possible, depending on controller. One drive gets parity, two drives get data on the first stripe. Second stripe puts parity on next drive, third stripe puts data on last drive. One drive's failure allows controller to create data out of two stripes combination of data and parity information. Lose a second drive, and data is killed.