One important piece of system software for clusters is the parallel file system. All current parallel file systems and parallel I/O libraries for cluster do not use standard server, thus it is very difficult to use these systems in heterogeneou environment. However, why use proprietary or special- purpose servers on the server end of a parallel filesystem when you have most of the necessary functionality in NFS servers already? This paper¹ describes the fault tolerance implemented in Expand (Expandable Parallel File System), a parallel file system based on NFS servers. Expand allows the transparent use of multiple NFS servers as a single file system, providing a single name pace. The different NFS servers are combined to create a distributed partition where files are stripped. Expand requires no changes to the NFS server and uses RPC operations to provide parallel acces to the same file. Expand is also independent of the client, because all operations are implemented using RPC and NFS protocol. Using this system, we can join heterogeneous server (Linux, Solaris, Window 2000, etc.) to provide a parallel and distributed partition. Fault tolerance is achieved using RAID techniques applied to parallel files. The paper describes the design of Expand and the evaluation of a prototype of Expand, using MPI-IO interface. This evaluation has been made in Linux clusters and compares Expand with PVFS.