A PARALLEL DISK STORAGE-SYSTEM FOR REAL-TIME MULTIMEDIA APPLICATIONS

We describe design and implementation of the RIO (randomized I/O) mult imedia object server which manages a set of parallel disks and support s real-time throughput and statistical delay guarantees. This storage subsystem was implemented as part of a multimedia information server s upporting multiple concurrent applications such as video on demand and 3D interactive virtual worlds. We discuss principal issues and innova tions involved in design and implementation of RIO storage system, pre senting experimental performance results measured on a prototype imple mentation. A multimedia data server must be ready to handle a variety of real-time object types (video, audio, 3D interactive virtual worlds , etc.) along with a nonreal-time workload component. Achieving simult aneously (1) high utilization and (2) low latency with high degree of certainty is the challenge. Our prototype system provides a statistica l guarantee of quality of service. Our experimental results show that it is possible to achieve a very small probability of exceeding a dead line (less than 10(-6)), with relatively high disk utilization (70-99% , in terms of fraction of the maximum disk capacity), together with re latively small delay bound ton the order of 0.5-1.5 s), using contempo rary disks. Results were achieved using random allocation of disk bloc ks and replication in conjunction with on-line load balancing. (C) 199 8 John Wiley & Sons, Inc.