An XOR-based Erasure-Recovered Algorithm for Tolerating Double Disk Failure in Disk Array Systems

C.-S. Tau (Taiwan)


Disk array, erasure-recovered algorithm, parity, RAID system, and XOR operation


This paper proposes an efficient erasure-recovered algorithm based on parity placement scheme, called Horizontal-Oblique Parity (HOP), for protecting against double disk failures in RAID-5 disk array systems. HOP keeps all data unencoded, and uses only exclusive-or (XOR) operations to compute parity. HOP is provably near optimal in computational complexity, both during encoding and reconstruction. It is optimal in the amount of redundant information stored and is sub-optimal in its accessing. HOP works within a single stripe of blocks of sizes normally used by file systems, databases, and disk arrays.

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