Increasingly, le systems for multiprocessors are designed with parallel access to multiple disks, to keep I/O from becoming a serious bottleneck for parallel applications. Although le system software can transparently provide high-performance access to parallel disks, a new le system interface is needed to facilitate parallel access to a le from a parallel application. We describe the di culties faced when using the conventional (Unix-like) interface in parallel applications, and then outline ways to extend the conventional interface to provide convenient access to the le for parallel programs, while retaining the traditional interface for programs that have no need for explicitly parallel le access. Our interface includes a single naming scheme, a multiopen operation, local and global le pointers, mapped le pointers, logical records, multi les, and logical coercion for backward compatibility. 1

Abstract. Improvements in the processing speed of multiprocessors are outpacing improvements in the speed of disk hardware. Parallel disk I/O subsystems have been proposed as one way to dose the gap between processor and disk speeds. In a previous paper we showed that prefetching and caching have the potentT"al to deliver the performance benefits of parallel file systems to parallel applications. In this paper we describe experiments with practical prefetching policies that base decisions only on on-line reference history, and that can be implemented efficiently. We also test the ability of those policies across a range of architectural parameters. Keywords: multiprocessor file systems, parallel I/O, file caching, prefetching 1.

Improvements in the processing speed of multiprocessors are outpacing improvements in the speed of disk hardware. Parallel disk I/O subsystems have been proposed as one way to close the gap between processor and disk speeds. Such parallel disk systems require parallel le system software to avoid performance-limiting bottlenecks. We discuss cache management techniques that can be used inaparallel le system implementation. We examine several writeback policies, and give results of experiments that test their performance. 1

Improvements in the processing speed of multiprocessors are outpacing improvements in the speed of disk hardware. Parallel disk I/O subsystems have been proposed as one way to close the gap between processor and disk speeds. Such parallel disk systems require parallel file system software to avoid performance-limiting bottlenecks. We discuss cache management techniques that can be used in a parallel file system implementation for multiprocessors with scientific workloads. We examine several writeback policies, and give results of experiments that test their performance.