Caching and Writeback Policies in Parallel File Systems

Improvements in the processing speed of multiprocessors are outpacing improvements in the speed of disk hardware. Parallel disk I/O subsystems have been proposed as one way to close the gap between processor and disk speeds. Such parallel disk systems require parallel file system software to avoid performance-limiting bottlenecks. We discuss cache management techniques that can be used in a parallel file system implementation. We examine several writeback policies, and give results of experiments that test their performance. 1 Introduction As computers grow more powerful, it becomes increasingly difficult to provide sufficient I/O bandwidth to keep them running at full speed for large problems, which may consume immense amounts of data. Disk I/O has always been slower than processing speed, and recent trends have shown that improvements in the speed of disk hardware are not keeping up with the increasing raw speed of processors. This widening access-time gap is known as the I/O crisi..