Rebuilding for Array Codes in Distributed Storage Systems

In distributed storage systems that use coding, the issue of minimizing the communication required to rebuild a storage node after a failure arises. The authors consider the problem of repairing an erased node in a distributed storage system that uses an EVENODD code. EVENODD codes are Maximum Distance Separable (MDS) array codes that are used to protect against erasures, and only require XOR operations for encoding and decoding. They show that when there are two redundancy nodes, to rebuild one erased systematic node, only 3/4 of the information needs to be transmitted. Interestingly, in many cases, the required disk I/O is also minimized.