RAID-6 is widely used to tolerate concurrent failures of any two disks in both disk arrays and storage clusters. Numerous erasure codes have been developed to implement RAID-6, of which MDS codes are popular. Due to t...
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ISBN:
(纸本)9781479908981
RAID-6 is widely used to tolerate concurrent failures of any two disks in both disk arrays and storage clusters. Numerous erasure codes have been developed to implement RAID-6, of which MDS codes are popular. Due to the limitation of parity generating schemes used in MDS codes, RAID-6-based storage systems suffer from low reconstruction performance. To address this issue, we propose a new class of XOR-based RAID-6 code (i.e., V-2-code), which delivers better reconstruction performance than the MDS RAID-6 code at low storage efficiency cost. V-2-code, a very simple yet flexible Non-MDS vertical code, can be easily implemented in storage systems. V-2-code's unique features include (1) lowest density, (2) steady length of parity chain, and (3) well balanced computation. We perform theoretical analysis and evaluation of the coding scheme under various configurations. The results show that V(2-)code is a well-established RAID-6 code that outperforms both X-code and code-M in terms of reconstruction time. V-2-code can speed up the reconstruction time of X-code by a factor of up to 3.31 and 1.79 under single disk failure and double disk failures, respectively.
X-code is one of the most important redundant array of independent disk （RAID）-6 codes which are capable of tolerating double disk failures. However, the code length of X-code is restricted to be a prime number, and...
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X-code is one of the most important redundant array of independent disk （RAID）-6 codes which are capable of tolerating double disk failures. However, the code length of X-code is restricted to be a prime number, and such code length restriction of X-code limits its usage in the real storage systems. Moreover, as a vertical RAID-6 code, X-code can not be extended easily to an arbitrary code length like horizontal RAID-6 codes. In this paper, a novel and efficient code shortening algorithm for X-code is proposed to extend X-code to an arbitrary length. It can be further proved that the code shortening algorithm maintains the maximum-distance-separable （MDS） property of X-code, and namely, the shortened X-code is still MDS code with the optimal space efficiency. In the context of the shortening algorithm for X-code, an in-depth performance analysis on X-code at consecutive code lengths is conducted, and the impacts of the code shortening algorithm on the performance of X-code in various performance metrics are revealed.
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