Efficient Repair Algorithm for Information Column of EVENODD(p,4) Codes

EVENODD codes are a class of binary maximum distance separable (MDS) array codes with p information columns and r parity columns such that any p out of p plus r columns can retrieve all the information bits stored in the p information columns. When a column fails, it is important to repair the failed column with repair bandwidth (the total amount of bits downloaded in repairing the failed column) as small as possible. In this paper, we first derive a lower bound on repair bandwidth of information column for EVENODD codes with 4 parity columns and then propose a repair algorithm to achieve as close to the lower bound as possible. We show that the repair bandwidth of information column of EVENODD codes with four parity columns by the proposed repair algorithm is less than that of the existing repair method for EVENODD codes with three or two parity columns.