Disk Storage and File Systems with Quality-of-Service Guarantees

Modern disk-storage systems have to accomplish the requirements of a variety of application classes. Applications that process continuous-media data such as video and audio streams require the storage system to guarantee sustained bandwidths. Interactive applications demand the storage system to ensure bounded response times, posing timing constraints on the execution of individual disk requests. Traditional timesharing applications may require both high throughput or overall short response times. With the described applications being more and more used together in todays computing systems, the disk-storage subsystems have to efficiently combine the different requirements of this application mix. In this thesis, I develop the design of a storage system that comprehensively addresses the various challenges posed by including the support for quality-of-service guarantees in disk-storage systems. The presented storage system provides three main properties. First, the admission control includes the support for statistical guarantees to increase the share of the disk bandwidth that can be utilized by the admission control. Second, the disk-request scheduling clearly separates the enforcement of real-time guarantees from the task to establish the optimal execution order of the requests, and it provides a flexible mechanism to combine the execution of requests with different quality-of-service requirements. Finally, the file system addresses both the needs of the former two elements of the storage system and of the various file types used by the applications by providing a flexible block-allocation policy and customized client interfaces. I show the implementation of the presented designs with the DROPS Disk-Storage System and I provide a detailed evaluation based on this implementation