This paper presents an adaptive erasure correction coding with lossless data compression to reduce the data read/write amount required to recover from single-and double-disk failures in disk arrays. The proposed method utilizes two types of redundancies to reduce the recovery cost, that is, data redundancy, meaning that data block may be compressed to a smaller size, and storage space redundancy, meaning that disk array may have unused storage space. To utilize these redundancies, the code rate of erasure correction coding is adaptively determined depending on the compressed data size and available storage space. Results of a simple simulation show that the proposed method can reduce the recovery cost without affecting the response time of failure-free operations. For a disk array of 6 disks with average compression ratio 0.6 and utilization ratio 0.7, the read data amount for single-failure recovery is reduced by a factor of 0.24.
['Haruhiko Kaneko']
Failure Recovery Cost Reduction of Disk Arrays Using Adaptive Erasure Correction Coding and Data Compression