RAC: A Soft-QoS Framework for Supporting Continuous Media Applications

Abstract

In this chapter, we present a novel disk admission control algorithm that exploits the degradability property of continuous media applications to improve the performance of the system. The algorithm is based on setting aside a portion of the resources, i.e., disk I/O bandwidth, as reserves and managing it intelligently so that the total utility of the system is maximized. This reserve-based admission control strategy (RAC) is a compromise between purely greedy and non-greedy strategy, and it leads to an efficient protocol that improves the performance of the system. While the protocol is simple for admission decision, it also results in better performance for the system by reserving some resources for the important future applications. The framework consists of two parts. One is the reserve-based admission control mechanism in which new streams, arriving during periods of congestion, are offered lower QoS, instead of being blocked. The other one is a resource scheduler for continuous media with dynamic resource allocation to achieve higher utilization than non-dynamic schedulers by effectively sharing available resources among contending streams and by reclamation, which is a scheduler-initiated negotiation to reallocate resources among streams to improve overall QoS.