Combining Low IO-Operations During Data Recovery with Low Parity Overhead in Two-Failure Tolerant Archival Storage Systems

Abstract—Archival data storage systems contain data that must be preserved over long periods of time but which are often unlikely to be accessed during their lifetime. The best strategy for such systems is to keep their disks powered-off unless they have to be powered up to access their contents, to reconstruct lost data, or to perform other disk maintenance tasks. Of all such tasks, reconstructing data after a disk failure is the one that is likely to have the highest energy footprint and the most impact on the overall power consumption of the array, because it typically involves powering up all the disks belonging to the same reliability stripe as the failed disk and keeping them running for considerable time at each occurrence. We investigate two two-failure tolerant disk layouts that have lower parity overhead than the number of disks read (and hence powered-on) for recovering data on lost drives would suggest