Architectures and algorithms for on-line failure recovery in redundant disk arrays

The performance of traditional RAID Level 5 arrays is, for many applications, unacceptably poor while one of its constituent disks is non-functional. This paper describes and evaluates mechanisms by which this disk array failure-recovery performance can be improved. The two key issues addressed are thedata layout, the mapping by which data and parity blocks are assigned to physical disk blocks in an array, and thereconstruction algorithm, which is the technique used to recover data that is lost when a component disk fails.