As use of network-attached storage (NAS) filers and large file servers has grown, so have the challenges of file-serving management, scalability and availability. What's needed is a way to provide scalable, highly available file services using inexpensive, industry-standard servers that can be added incrementally on demand, while retaining the management simplicity of a single server and a single pool of exported file systems. This paper describes innovative NAS Cluster software that enables incremental scaling of file services, use of standard servers and storage, 6:1 price/performance and 5x performance advantage over traditional NAS, and fault tolerance at no additional cost.