基于局部冗余混合编码的故障快速恢复方法

最大距离可分（MDS）码中校验块均为全局校验块，重构链长度随着存储系统规模扩大而增长，重构性能逐渐降低。针对上述问题提出一种新型的非最大距离可分（Non-MDS）码：局部冗余混合编码Code-LM（s，c）。首先，为缩小重构链长度，任意条带单元组内只有局部校验块，分别为组内水平校验块和水平对角校验块，并设计了局部冗余混合编码的校验布局；然后，根据不同校验块的生成规则，设计了失效数据块的4种重构方式，不同失效块的重构链具有公共块；最后，根据两个故障磁盘所在条带单元组距离不同，将双盘故障分为3种情况，并设计了对应的重构算法。理论分析和实验结果表明，存储规模相同时，与RDP相比，Code-LM（s，c）的单盘重构时间和双盘重构时间可减少84%和77%；与V²-Code相比，Code-LM（s，c）的单盘重构时间和双盘重构时间可减少67%和73%。因此局部冗余混合编码可支持故障磁盘快速恢复，提高存储系统可靠性。

Fast failure recovery method based on local redundant hybrid code

The parity blocks of the Maximum-Distance-Separable （MDS） code are all global parity blocks. The length of the reconstruction chain increases with the expansion of the storage system， and the reconstruction performance gradually decreases. Aiming at the above problems， a new type of Non-Maximum-Distance-Separable （Non-MDS） code called local redundant hybrid code Code-LM（s，c） was proposed. Firstly， two types of local parity blocks called horizontal parity block in the strip-set and horizontal-diagonal parity block were added in any strip-sets to reduce the length of the reconstruction chain， and the parity layout of the local redundant hybrid code was designed. Then， four reconstruction formulations of the lost data blocks were designed according to the generation rules of the parity blocks and the common block existed in the reconstruction chains of different data blocks. Finally， double-disk failures were divided into three situations depending on the distances of the strip-sets where the failed disks located and the corresponding reconstruction methods were designed. Theoretical analysis and experimental results show that with the same storage scale， compared with RDP （Row-Diagonal Parity）， the reconstruction time of CodeM（s，c） for single-disk failure and double-disk failure can be reduced by 84% and 77% respectively； compared with V²-Code， the reconstruction time of Code-LM（s，c） for single-disk failure and double-disk failure can be reduced by 67% and 73% respectively. Therefore， local redundant hybrid code can support fast recovery from failed disks and improve reliability of storage system.