We develop a holistic framework for adaptively scheduling asynchronous requests in distributed file systems. The system is holistic in that it manages all resources, including network bandwidth, server I/O, server CPU, and client and server memory utilization. It accelerates, defers, or cancels asynchronous requests in order to improve application-perceived performance directly. We employ congestion pricing via online auctions to coordinate the use of system resources by the file system clients so that they can detect shortages and adapt their resource usage. We implement our modifications in the Congestion-Aware Network File System (CA-NFS), an extension to the ubiquitous network file system (NFS). Our experimental result shows that CA-NFS results in a 20% improvement in execution times when compared with NFS for a variety of workloads.

We present the network file system with cluster delegation (NFS-CD), an enhancement to the NFSv4 that reduces server load and increases the scalability of distributed file systems in computing clusters. The cluster delegation feature of NFS-CD allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster delegation, we implement a fast-commit primitive, cooperative caching, and the ability to recover the uncommitted updates of a failed computer. NFS-CD supports both read and write operations in the cooperative cache without degrading the consistency model of NFSv4. We have implemented NFS-CD by modifying the Linux NFSv4 client only. Because the server remains unchanged, NFS-CD preserves the simple administration model of NFSv4 and interoperates with standard NFS clients. NFS-CD offers improved performance when compared to NFSv4 at the expense of slightly weaker reliability guarantees. An experimental evaluation of our implementation, using industry standard benchmarks and application workloads, reveals that NFS-CD reduces server load by more than half. It also demonstrates that under most workloads, file systems must support writes to the cooperative cache to achieve scale.

We present cluster delegation, an enhancement to the NFSv4 file system, that improves both performance and recoverability in computing clusters. Cluster delegation allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster delegation, we implement a fast commit primitive, cooperative caching, and the ability to recover the uncommitted updates of a failed computer. Cluster delegation supports both read and write operations in the cooperative cache, while preserving the consistency guarantees of NFSv4. We have implemented cluster delegation by modifying the Linux NFSv4 client and show that it improves client performance and reduces server load by more than half.