As the PC cluster has grown in popularity as a parallel computing platform, the demand for system software for this platform has grown as well. One common piece of system software available for many commercial parallel machines is the parallel file system. Parallel file systems offer higher I/O performance than single disk or RAID systems, provide users with a convenient and consistent name space across the parallel machine, support physical distribution of data across multiple disks and network entities (I/O nodes), and typically include additional I/O interfaces to support larger files and control of file parameters. As Linux clusters have matured as platforms for low-cost, high-performance parallel computing, software packages to provide many key services have emerged, especially in areas such as message passing and networking. One area devoid of support, however, has been parallel file systems, which are critical for high-performance I/O on such clusters. PVFS is intended both as a high-performance parallel file system that anyone can download and use and as a tool for pursuing further research in parallel I/O and parallel file systems for Linux clusters.