R5X0: An Efficient High Distance Parity-Based Code with Optimal Update Complexity

We present a new class of array codes based on a generalization of the RAID5 XOR parity code. The R5X0(n, r, p) code protects an array of n data disks and p parity disks with r symbols per column from as many as p arbitrary column erasures. Decoding and encoding in R5X0 is computed using only XOR and cyclic shift operations. R5X0 is a simple geometric generalization of RAID5 and has optimal update complexity (the number of parity symbols affected by a single data symbol is exactly p) and asymptotically optimal storage efficiency for its distance. The only geometric constraint on the R5X0 layout is that r ≥ (p− 1) · n.