Comparison of RAID-6 Erasure Codes

Coding techniques for RAID-6 storage systems, providing a double fault-tolerance, are varied. They all come with their respective benefits and limitations. In this paper, we compare the characteristics of five prominent erasure codes. We show that the general-purpose Reed-Solomon codes, either based on Vandermonde or Cauchy matrices, are outperformed by Array codes (i.e. EVENODD, RDP) which are specifically designed for RAID-6 storage systems. However geometrical codes such as the Mojette erasure code show even better performances at the cost of a slight extra storage overhead. We outline the differences between these codes in terms of encoding, updating and decoding complexity. We believe that such an analysis can be valuable to system designers to figure out which code would best suit their requirements.

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