低编译复杂度的双容错阵列码

Double fault tolerant array code with low compilation complexity

纠删码技术是独立磁盘冗余阵列-6(RAID-6)的双容错能力的底层实现技术,它的性能是左右RAID-6性能的重要因素。针对RAID-6中常用阵列纠删码的I/O不平衡和数据恢复速度慢的问题,提出一种基于异或(XOR)的混合阵列码——J码(J-code)。J-code采用新的校验生成规则,首先,利用原始数据构造的二维阵列计算出对角校验位并构造新的阵列;然后,利用新阵列中数据块之间的位置关系计算得到反对角校验位。此外,J-code将原始数据与部分校验位存储于同一磁盘,能减少编译码过程中的异或(XOR)操作次数和单盘恢复过程中读取数据块的个数,从而降低编译码复杂度和单盘故障修复的I/O成本,缓解磁盘热点集中现象。仿真实验结果表明,相较于RDP(Row-Diagonal Parity)、EaR(Endurance-aware RAID-6)等阵列码,J-code的编码时间减少了0.30%~28.70%,单磁盘故障和双磁盘故障的修复用时分别减少了2.23%~31.62%和0.39%~36.00%。

Erasure coding is the underlying implementation technology of double fault tolerance for Redundant Array of Independent Disks-6(RAID-6),and the performance of erasure code is one of the important factors affecting the performance of RAID-6.Aiming at the problems of I/O imbalance and slow data recovery of array erasure codes commonly used in RAID-6,an Exclusive OR(XOR)based hybrid array code was proposed,namely J-code.A new parity check generation rule was adopted by J-code.Firstly,two-dimensional array constructed from the original data was used to calculate the diagonal parity bits and construct a new array.Then,the positional relationship between the data blocks in the new array was used to calculate the anti-diagonal parity bits.Besides,the original data and part of the parity bits were stored by J-code on the same disk,which reduced the number of XOR operations in the process of encoding and decoding as well as the number of data blocks read in the recovery process of a single disk,thereby reducing the complexity of encoding and decoding as well as the I/O cost for repairing a single disk,and alleviating the phenomenon of disk hotspot concentration.Simulation results show that compared with array codes such as RDP(Row-Diagonal Parity)and EaR(Endurance-aware RAID-6),J-code has the encoding time reduced by 0.30%to 28.70%,the single disk failure repair time reduced by 2.23%to 31.62%,and the double disk failure repair time reduced by 0.39%to 36.00%.