Providing QOS guarantees for disk

In this paper, we address the problem of providing diierent levels of performance guarantees or quality-of-service (QOS) for disk I/O. We classify disk requests into three categories based on the provided level of service. We propose an integrated scheme that provides diierent levels of performance guarantees in a single system. We propose and evaluate a mechanism for providing deterministic service for Variable Bit Rate (VBR) streams at the disk. We will show that through proper admission control and bandwidth allocation, requests in diierent categories can be ensured of performance guarantees without getting impacted by requests in other categories. We evaluate the impact of scheduling policy decisions on the provided service. We also quantify the improvements in stream throughput possible by using statistical guarantees instead of deterministic guarantees in the context of the proposed approach.