台北科技大学：《计算机网络》（英文版） NP04 24(comer)

Network file System Concepts Chuan-Ming liu Computer Science and Information Engineering National Taipei university of Technology Taipei TAIWAN

1 Network File System Concepts Chuan-Ming Liu Computer Science and Information Engineering National Taipei University of Technology Taipei, TAIWAN

Outline DINTRODUCTION DREMOTE FILES OREVIEW OF THE UNIX FILE SYSTEM DNFS OVERVIEW DFILE HANDLE DSTATELESS SREVER D MOUNT AND TRANSPORT PROTOCOLS

2 Outline INTRODUCTION REMOTE FILES REVIEW OF THE UNIX FILE SYSTEM NFS OVERVIEW FILE HANDLE STATELESS SREVER MOUNT AND TRANSPORT PROTOCOLS

Introduction D This chapter describes the general concept of remote file access and reviews the concepts underlying a particular remote access mechanism D Because the remote file access mechanism derives many ideas and details from the underlying Os, the chapter reviews the Linux file system and the semantics of file operations

3 Introduction This chapter describes the general concept of remote file access and reviews the concepts underlying a particular remote access mechanism Because the remote file access mechanism derives many ideas and details from the underlying OS, the chapter reviews the Linux file system and the semantics of file operations

Outline DINTRODUCTION DREMOTE FILES OREVIEW OF THE UNIX FILE SYSTEM DNFS OVERVIEW DFILE HANDLE DSTATELESS SREVER D MOUNT AND TRANSPORT PROTOCOLS

4 Outline INTRODUCTION REMOTE FILES REVIEW OF THE UNIX FILE SYSTEM NFS OVERVIEW FILE HANDLE STATELESS SREVER MOUNT AND TRANSPORT PROTOCOLS

Remote file access vs Transfer D File transfer services: invoked by users D File access services: invoked by application programs to transfer one small block of data at a time

5 Remote File Access vs. Transfer File transfer services: invoked by users File access services: invoked by application programs to transfer one small block of data at a time

Remote file access vs Transfer(Cont) DThe server checks each request to verify that the client is authorized to access the specified file, performs the specified operation, and returns a result to the client The Network File System, defined by Sun Microsystems, is a remote file access mechanism that has been widely accepted through the computer industry

6 Remote File Access vs. Transfer (Cont.) The server checks each request to verify that the client is authorized to access the specified file, performs the specified operation, and returns a result to the client The Network File System, defined by Sun Microsystems, is a remote file access mechanism that has been widely accepted through the computer industry

Operations on Remote Files DNFS provides the same operations(open read, write, seek, and close) on remote files that one expects to use on local files Seek to a specified position in the file

7 Operations on Remote Files NFS provides the same operations (open, read, write, seek, and close) on remote files that one expects to use on local files seek to a specified position in the file

File access among Heterogeneous Computers )A remote file access service must handle differences in the way the client and server systems name files, denote paths through directories and store information about files D The file access software must accommodate differences in the semantic interpretation of file operations ONFS was designed to accommodate heterogeneous computer systems

8 File Access Among Heterogeneous Computers A remote file access service must handle differences in the way the client and server systems name files, denote paths through directories, and store information about files The file access software must accommodate differences in the semantic interpretation of file operations NFS was designed to accommodate heterogeneous computer systems

Outline DINTRODUCTION DREMOTE FILES OREVIEW OF THE UNIX FILE SYSTEM DNFS OVERVIEW DFILE HANDLE DSTATELESS SREVER D MOUNT AND TRANSPORT PROTOCOLS

9 Outline INTRODUCTION REMOTE FILES REVIEW OF THE UNIX FILE SYSTEM NFS OVERVIEW FILE HANDLE STATELESS SREVER MOUNT AND TRANSPORT PROTOCOLS

nFS and unix file semantics )The nFS designers adopted UNIX file system semantics when defining the meaning of individual operations O Understanding the original UNIX file system is essential to understanding NFS because NFs uses the uniX file system terminology and semantics

10 NFS and Unix File Semantics The NFS designers adopted UNIX file system semantics when defining the meaning of individual operations Understanding the original UNIX file system is essential to understanding NFS because NFS uses the UNIX file system terminology and semantics