RAID Level 2: Memory-Style Error-Correcting-Codes (ECC) with bit striping.
RAID Level 3: Bit-Interleaved Parity
a single parity bit is enough for error correction, not just detection, since we know which disk has failed
When writing data, corresponding parity bits must also be computed and written to a parity bit disk
To recover data in a damaged disk, compute XOR of bits from other disks (including parity bit disk)