The NFS environment includes the NFS client system(s), the mix of networks available, the NFS server system(s), and the manner in which they are configured. While this guide is intended for z/OS NFS, it is important to know the performance limitations within the NFS environment to determine the necessity of tuning z/OS NFS.

NFS client systems range from single user desktop personal computers to large scale processors with many users. These NFS client systems typically support multiple applications as well. Clearly, the NFS client system resources will be shared between its users and/or applications. These resources include available physical storage, memory, processing capability, and network access. The NFS client is one application, with a possibility for many users, that must share the memory, processing, and network resources in exchange for providing access to additional physical storage on other systems. The degree to which the NFS client application must share such resources will affect performance for NFS client users and applications.

The NFS server system, like the NFS client system, must share resources with other users and applications. NFS server application performance will be affected by the amount of contention over system resources and by the priority established for the NFS server application. The overall performance of an NFS server is also influenced by the number of NFS clients for which it provides services.

The network(s) over which NFS clients access NFS servers also affect overall performance in the NFS environment. Such networks can be homogenous, consisting of a single network medium, or heterogeneous, consisting of a mix of network mediums. Each network medium type has an expected maximum capacity, or bandwidth. For instance, the capacity of a Fast Ethernet Ring network may be 16 megabits per second (Mbps) or 4 Mbps, and the capacity of a Fiber Distributed Data Interface (FDDI) network is 100 Mbps. When different network mediums are combined in a more complex network environment, the capacity for a fixed route over the network is limited by the network segment with the smallest capacity. For example, a route over a network consisting of both 4 and 16 Mbps Token Rings and a FDDI backbone will have a maximum capacity equivalent to that of the Token Ring, or 4 Mbps. When bridges, routers, and gateways are included in a network configuration, their capacity must also be considered. Such devices must also be considered when tuning performance in a network environment, particularly if a device does not support increased network buffer sizes.