B: Disk Array Data Layout Tolerating Multiple Failures

We present B a novel data layout method for tolerating multiple disk failures within disk arrays. In a disk array with 2n disks, B tolerates at most 2(n - 1) simultaneous failures; reconstruction work is spread over the surviving disks using only exclusive-or operations. The data layout is based upon B array-codes; our approach provides an efficient software implementation. B utilizes the minimal amount of redundant storage space. Our detailed performance comparison with RAID-5 and EVENODD shows B read operations to be very competitive especially in the presence of failures; B write operations are more expensive than RAID-5 and EVENODD write operations. In the presence of failures, the performance gradually degrades as the number of failures increases.