Patent ID: 8443264

Claim:
A disk array apparatus, comprising: a plurality of magnetic disks; and a RAID controller that is configured to: generate redundancy data for host data received from a host apparatus by a primitive polynomial of Galois extension field, said redundancy data being usable to restore one of said plurality of magnetic disks; generate a redundancy code for said host data and a redundancy code for said redundancy data, said redundancy codes being usable to detect an error of a corresponding one of said host data and said redundancy data, said redundancy codes each being a cyclic code based on a generating polynomial which is identical to said primitive polynomial, said redundancy code for said host data being calculated from said host data by said generating polynomial and said redundancy code for said redundancy data being calculated from said redundancy code for said host data and write said host data and said redundancy data to said plurality of magnetic disks.