Design and evaluation of data access strategies in a high performance multimedia-on-demand server

One of the key components of a multi user multimedia on demand system is the data server. Digitization of traditionally analog data such as video and audio, and the feasibility of obtaining network bandwidths above the gigabit per second range are two important advances that have made possible the realization, in the near future, of interactive distributed multimedia systems. Secondary-to-main memory I/O technology has not kept pace with advances in networking, main memory and CPU processing power. Consequently, the performance of the server has a direct bearing on the overall performance of such a system. We develop a model for the architecture of a server for such a system. Parallelism of data retrieval is achieved by striping the data across multiple disks. The performance of any server ultimately depends on the data access patterns. Two modifications of the basic retrieval algorithm are presented to exploit data access patterns in order to improve system throughput and response time. A complementary information caching optimization is discussed. Finally, we present performance results of these algorithms on the IBM SP1 and Intel Paragon parallel computers.