Using storage class memories to increase the reliability of two-dimensional RAID arrays

Two-dimensional RAID arrays maintain separate row and column parities for all their disks. Depending on their organization, they can tolerate between two and three concurrent disk failures without losing any data. We propose to enhance the robustness of these arrays by replacing a small fraction of these drives with storage class memory devices, and demonstrate how such a pairing is several times more reliable than relying on conventional disks alone, or simply augmenting popular redundant layouts. Depending on the ratio of the failure rates of these two devices, the substitution can double or even triple the mean time to data loss (MTTDL) of each array.