STAR : An Efficient Coding Scheme for Correcting Triple Storage Node Failures

Abstract

Proper data placement schemes based on erasure correcting codes are one of the most important components for a highly available data storage system. For such schemes, low decoding complexity for correcting (or recovering) storage node failures is essential for practical systems. In this paper, we describe a new coding scheme, which we call the STAR code, for correcting triple storage node failures (erasures). The STAR code is an extension of the double-erasure-correcting EVENODD code and a modification of the generalized triple-erasure-correcting EVENODD code. The STAR code is an Maximum Distance Separable (MDS) code and thus is optimal in terms of node failure recovery capability for a given data redundancy. We provide detailed STAR code decoding algorithms for correcting various triple node failures. We show that the decoding complexity of the STAR code is much lower than those of existing comparable codes; thus, the STAR code is practically very meaningful for storage systems that need higher reliability.