Providing QOS guarantees for disk I/O

In this paper, we address the problem of providing different levels of perf ormance guarantees or quality of service for disk I/O. We classify disk req uests into three categories based on the provided level of service. We prop ose an integrated scheme that provides different levels of performance guar antees in a single system. We propose and evaluate a mechanism for providin g deterministic service for variable-bit-rate streams at the disk. We will show that, through proper admission control and bandwidth allocation, reque sts in different categories can be ensured of performance guarantees withou t getting impacted by requests in other categories. We evaluate the impact of scheduling policy decisions on the provided service. We also quantify th e improvements in stream throughput possible by using statistical guarantee s instead of deterministic guarantees in the context of the proposed approa ch.