A New Non-MDS RAID-6 Code to Support Fast Reconstruction and Balanced I/Os

Abstract

RAID-6 is widely applied to tolerate double concurrent disk failures in both disk arrays and storage clusters. Among numerous erasure codes developed to implement RAID-6, Maximum Distance Separable (MDS) Codes are highly popular. Owing to the limitation of parity generating schemes used in MDS codes, RAID-6-based storage systems suffer from unbalance I/Os and low reconstruction performance. Out of consideration for high performance and reliability, we propose a new class of XOR-based RAID-6 code (i.e. |$V^{2}$|-Code), which improves both load balancing and reconstruction performance of the MDS RAID-6 codes. |$V^{2}$|-Code, a very simple yet flexible Non-MDS vertical code, can be easily implemented and deployed in storage systems. |$V^{2}$|-Code's unique features include lowest density code, steady parity chain length and well-balanced computation. We perform theoretical analysis and empirical evaluation of the coding scheme by running a wide range of workload under various configurations. Experimental results show that |$V^{2}$|-Code outperforms four popular codes (i.e. EVENODD, RDP, X-Code and Code-M) in terms of load balancing and reconstruction time. In the single-disk-failure and double-disk-failure cases, |$V^{2}$|-Code can speed up the reconstruction time of X-Code by a factor of up to 3.31 and 1.79, respectively.