UNIX Filesystems: Evolution, Design, and Implementation

Distributed Filesystems

Unlike local filesystems where the storage is physically attached and only accessible by processes that reside on the same host machine, distributed filesystems allow access to files on a remote machine through use of a well-defined protocol. Distributed filesystems employ a client/server model where a single filesystem server can serve files to multiple clients.

Regardless of the type of distributed filesystem, one goal that is absolutely essential to all of these filesystems is the need to provide UNIX file semantics when accessing remote files from the client.

There have been numerous distributed filesystems developed for UNIX over the last 20 years. Many of them have come and gone. The most successful distributed filesystem by far is the Sun Network Filesystem (NFS) which appeared in the mid 1980s. Although not as feature-rich as filesystems such as the DCE Distributed File Service (DFS), the simplicity of the NFS protocol, together with the fact that the NFS protocol is in public domain, resulted in it being ported to many different operating systems, UNIX and non-UNIX alike.

The following sections describe some of the main UNIX distributed filesystems with particular emphasis on NFS.

The Network File System (NFS)

With the advent of networks providing connectivity between computers, it became feasible to provide interfaces through which user programs could access files across a network using the same mechanisms by which they accessed files on a local ...