This mirroring can be combined with RAID 0, giving striped disks that are mirrored. Although this offers the high performance of RAID 0 and redundancy, it is much more expensive and typically not seen except in environments where cost just doesn't matter. This is striping, but with some drives storing ECC data. As all modern drives implement ECC information themselves, there's no particular advantage to this configuration. RAID 3 Stripes data across multiple drives, but dedicates one drive to parity information.
Data is read from all drives at once.
This uses the imbedded ECC data to detect errors, and recovers data using the parity information. RAID 3 can give high performance in dedicated situations where large amounts of data need to be read quickly. It requires synchronized spindle drives and really doesn't perform well in multi-user situations and therefore is not usually seen except in unusual and very specialized circumstances. You can see how this works by using the Javascript Bit Twiddler . For example, if you XOR the values 12 and 15, you'll get 3.