A parallel disk storage system for real-time multimedia applications

We describe design and implementation of the RIO (randomized I/O) multimedia object server which manages a set of parallel disks and supports real-time throughput and statistical delay guarantees. This storage subsystem was implemented as part of a multimedia information server supporting multiple concurrent applications such as video on demand and 3D interactive virtual worlds. We discuss principal issues and innovations involved in design and implementation of RIO storage system, presenting experimental performance results measured on a prototype implementation. 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 simultaneously (1) high utilization and (2) low latency with high degree of certainty is the challenge. Our prototype system provides a statistical guarantee of quality of service. Our experimental results show that it is possible to achieve a very small probability of exceeding a deadline (less than 10−6), with relatively high disk utilization (70–99%, in terms of fraction of the maximum disk capacity), together with relatively small delay bound (on the order of 0.5–1.5 s), using contemporary disks. Results were achieved using random allocation of disk blocks and replication in conjunction with on-line load balancing. © 1998 John Wiley & Sons, Inc.