Parallel file systems provide high performance disk access, which is crucial for many scientific and commercial applications.In this paper, we explore the current state of the art of parallel file systems for PC clusters.To do so, we evaluate the I/O performance of Intel PFS, a commercial file system for ASCI Red, and PVFS, an open-source file system for Linux clusters.Our study shows that parallel file systems for PC clusters have come a long way.While there is still room for improvements, high performance disk access on PC clusters is becoming a reality.Three and a half years after I/O throughputs of more than 1 Gigabyte/sec have been achieved for the first time (with Intel PFS on ASCI Red), PVFS can now deliver this level of I/O performance on PC clusters.