An integrated prefetching/caching scheme in multimedia servers

Abstract

Advances in storage and networking technologies have made on-demand multimedia services prevalent these days. To provide numerous concurrent users with such high-quality services, it is essential for storage systems to support sufficient I/O bandwidth for delivering multimedia data on time. Two data buffering techniques, prefetching and interval caching, have improved I/O performance by keeping data blocks in memory for future accesses when handling multimedia data with sequential access patterns. However, they have been addressed separately since it is challenging to determine whether it is better to prefetch or to cache each new stream depending on specific situations. Prefetching too many blocks or caching too long intervals may exhaust the cache space quickly. In this paper, we propose a scheme, called Integrated Prefetching/Caching (IPC), to simultaneously take benefit of both prefetching and interval caching using dynamic threshold values. The IPC schedules incoming streaming requests so that utilization of both cache space and disk bandwidth can be maximized. As a result, the IPC can continue to improve the performance without saturation as system resources are added. By simulation experiments, we show that IPC increases the number of concurrent streams significantly, compared to when either prefetching or caching is employed alone.