by R. Sandberg, USENIX 1986.
Abstract:
The Sun Network Filesystem (NFS) provides transparent, remote access to filesystems. Unlike many other remote filesystem implementations under UNIX, NFS is designed to be easily portable to other operating systems and machine architectures. It uses an External Data Representation (XDR) specification to describe protocols in a machine and system independent way. NFS is implemented on top of a Remote Procedure Call package (RPC) to help simplify protocol definition, implementation, and maintenance.
In order to build NFS into the UNIX kernel in a way that is transparent to applications, we decided to add a new interface to the kernel which separates generic filesystem operations from specific filesystem implementations. The “filesystem interface” consists of two parts: the Virtual File System (VFS) interface defines the operations that can be done on a filesystem, while the virtual node (vnode) interface defines the operations that can be done on a file within that filesystem. This new interface allows us to implement and install new filesystems in much the same way as new device drivers are added to the kernel.
In this paper we discuss the design and implementation of the filesystem interface in the UNIX kernel and the NFS virtual filesystem. We compare NFS to other remote filesystem implementations, and describe some interesting NFS ports that have been done, including the IBM PC implementation under MS/DOS and the VMS server implementation. We also describe the user-level NFS server implementation which allows simple server ports without modification to the underlying operating system. We conclude with some ideas for future enhancements.
In this paper we use the term server to refer to a machine that provides resources to the network; a client is a machine that accesses resources over the network; a user is a person “logged in” at a client; an application is a program that executes on a client; and a workstation is a client machine that typically supports one user at a time.
Link to the full paper:
