Concepts and usage of NFS servers (1)

NFS is a major application of networks and computers. We also briefly introduced the NFS server in the previous article. Here we will explain the basic content systematically. Help you understand this part. NFS is an integral part of Distributed Computer systems. It can share and assemble remote file systems on Heterogeneous Networks.

NFS Introduction

Developed by SUN, NFS has become a standard for file services (RFC1904, RFC1813 ). its biggest function is to allow computers of different operating systems to share data over the network, so it can also be viewed as a file server, as shown in Figure 1-1. NFS provides communication between Windows, Linux, and UNIX and Linux in addition to Samba.

Figure 1-1 NFS can be used as a file server

The client PC can mount the directory provided by the NFS server. After mounting, the directory looks like a local disk partition, you can use cp, cd, mv, rm, df, and other disk-related commands. NFS has its own protocol and port number, but when transmitting data or other related information, the NFS server uses a Remote Procedure Call, RPC) to assist the running of NFS servers.

Why NFS?

NFS aims to allow computers to share resources. In 1980s, the computer industry developed rapidly. Low-Cost CPU and client/server technologies have promoted the development of the distributed computing environment. however, when the processor price drops, the price of large-capacity storage systems remains high. therefore, a certain mechanism must be used to make full use of the performance of a single processor while allowing the computer to share storage resources and data, so NFS came into being.

NFS Protocol

With NFS, the client can transparently access the file system on the server, which is different from the FTP protocol that provides file transmission. FTP will generate a complete copy of the file. NFS only accesses part of the file referenced by one process, and the purpose is to make the access transparent. this means that any client program that can access a local file can access an NFS file without any modification.

NFS is a client/server application constructed using SunRPC. Its client sends an RPC request to an NFS server to access the files. although this work can be implemented by a general user process, that is, the NFS client can be a user process that explicitly calls the server, and the server can also be a user process. NFS is generally not implemented in this way for two reasons. first, access to an NFS file must be transparent to the client. Therefore, NFS client calls are performed by the client operating system on behalf of the user process. Secondly, for efficiency considerations, the NFS server is implemented in the server operating system. if the NFS server is a user process, each client request and server response includes read and write data) will have to switch between the kernel and the user process, which is too costly. the NFS 3rd Protocol was released in 1993. Figure 1-2 shows a typical structure of an NFS client and an NFS server.