A study of I/O system organizations

With the increasing processing speeds, it has become important to design powerful and efficient I/O systems. In this paper, we look at several design options in designing an I/O system and study their impact on the performance. Specifically, we use trace driven simulations to study a disk system with a nonvolatile cache. Some of the considered design parameters include the cache block size, the fetch size, the cache size and the disk access policy. We show that decoupling the fetch size and the cache block size results in significant performance improvements. A new write-back policy is presented that is shown to offer significant performance benefits. We show that optimal block size in a two-level memory hierarchy is dependent only on the latency, data rate product of the second level as previously conjectured. We also present results showing the effect of a split access operation of a disk read/write head.