Many applications, ranging from simple utilities to databases, manipulate data too large or infrequently used to be reliably found in memory caches. Due to the huge disparity between processor speeds and disk access times, these disk-bound applications tend to waste a disproportionate percentage of their execution times waiting for disk requests to complete. We can hide disk latency from these applications by taking advantage of under-utilized I/O resources to perform prefetching. To be effective, however, prefetching requires timely and accurate information about what data will be needed in the future. From the Series:CSE Colloquia - 2000