A QoS degradation policy for revenue maximization in fault-tolerant multi-resolution video servers

Video servers are highly vulnerable to disk failures because they employ large-scale disk arrays to support many clients and multimedia contents. To cope with such a structural weakness, they reserve a significant portion of their resource contingent on disk operability, leading to under-utilization in normal operating mode. The paper addresses the improvement of resource utilization in fault-tolerant multi-resolution video servers. For this purpose, we propose a QoS degradation method and an admission control algorithm to maximize the system performance measured as revenue while guaranteeing every admitted client the minimum quality level in the event of disk failure. Our scheme exploits the multi-resolution property of video streams, and achieves graceful degradation at near-optimal level when the disk fails. Simulation results show that, in the best case, our proposed technique almost doubles the number of clients admitted for video service by greatly enhancing the resource utilization rates.