Abstract: A system for improving a performance of a write process in an exemplary RAID system reduces a number of IOs required for a short write in a RAID algorithm by using a replicated-parity drive. Parity is stored on the parity portion of the disk drives. A replicated-parity drive comprises all the parity information. Parity information for each parity drive is co-located or mirrored on the replicated-parity portion of the disk drives for fast access during a read portion of the read-modify-write process. Consequently, the system accesses parity data with one seek, as opposed to P seeks in a conventional disk array system utilizing P parity drives.

Abstract: A fault-tolerant system for storage arrays has constraints on the number of data from which each redundancy value is computed. The fault-tolerant system has embodiments that are supported on small array sizes to arbitrarily large array sizes, and can tolerate a large number T of failures. Certain embodiments can tolerate many instances of more than T failures. The fault-tolerant system has efficient XOR-based encoding, recovery, and updating algorithms and has simple redundancy formulas. The fault-tolerant system has improved IO seek costs for certain multiple-element sequential host updates.

Abstract: A recovery enabling system for storage arrays is a high distance generalization of RAID-5 with optimal update complexity and near optimal storage efficiency. The recovery enabling system utilizes presets, data cells with known values that initialize the reconstruction process. The presets allow resolution of parity equations to reconstruct data when failures occur. In one embodiment, additional copies of the layout of the recovery enabling system are packed onto the same disks to minimize the effect of presets on storage efficiency without destroying the clean geometric construction of the recovery enabling system. The recovery enabling system has efficient XOR-based encoding, recovery, and updating algorithms for arbitrarily large distances, making the recovery enabling system an ideal candidate when storage-efficient reliable codes are required.