Prioritized admission strategies to improve user-perceived performance in interactive VOD servers

In the past, much emphasis has been given to the data throughput of VOD ser vers. In Interactive Video-on-Demand (IVOD) applications, such as digital l ibraries, service availability and response times are more visible to the u ser than the underlying data throughput. Data throughput is a measure of ho w efficiently resources are utilized. Higher throughput may be achieved at the expense of deteriorated user-perceived performance metrics such as prob ability of admission and queuing delay prior to admission. In this paper, w e propose and evaluate a number of strategies to sequence the admission of pending video requests. Under different request arrival rates and buffer ca pacities, we measure the probability of admission, queueing delay and data throughput of each strategy. Results of our experiments show that simple hy brid strategies can improve the number of admitted requests and reduce the queuing time, without jeopardizing the data throughput. The techniques we p ropose are independent of the underlying disk scheduling techniques used. S o, they can be employed to improve the user-perceived performance of VOD se rvers, in general.