There are three types of clients in a
heterogeneous computing environment: diskless, dataless, and
datashare. A diskless client has no mass storage of its own.
All file access is provided by the distributed file system.
A diskless client boots, loads applications, and stores its
data on servers. A dataless client has only enough local
mass storage to enable it to boot and perhaps, load
applications. All of its data is kept on servers. A
datashare client can function more autonomously. It has some
applications and some data stored locally but, at the same
time, may have some data and applications stored remotely.
Figure 
shows a dataless client which uses a
single-tree file system/device model which is
attached to a server which uses a device based file system/device
model. The files in /users/Jane on the client
appear to be local but actually reside on the server.
Although the distributed file system in a heterogeneous computing environment is available over a large geographic area, as a practical matter, clients typically attach to servers which are close geographically, such as, within the same building or building complex. This is because most long distance network links operate at much slower speeds (e.g., 1.5 Megabits) than short distance links (e.g., 10 Megabits). The convenience of a distributed file system is diminished by slow speed communication.
A common solution to this problem is first to perform a file transfer over low speed links to local (i.e., geographically close) servers where clients have higher speed access. Then, clients may have transparent access at suitable speeds. For the purpose of file transfer, files are referenced in the file system/device model of the server rather than the client. A file reference is usually of the form: (network-node-name, file-reference).