Alternatives Of Network File System Essay, Research Paper
CONTENTS OF THE REPORT
List of contents???????????????.. 1
The introduction??????????????? 2
Sun Microsystems provides NFS version 4 ???? 5
The relation between the NFS server and
Client file systems?????????????? 6
Architecture of NFS????????????? 8
Alternative for NFS????????????? 9
What is CIFS (SMP)????..???????? 9
SMB Clients and Servers Currently
Available ????????????????? 10
comparison between NFS and CIFS(SMP)???????????????? 11
Conclusion????????????????. 15
Bibliography???????????????.. 17
Introduction
Since human beings have used Computers , the request of being rich ,and getting more information quicker than before has increased . Have you ever found yourself rushing from one computer to another in your office or home ,attending to several different jobs at various location? Or do you often find yourself moving files that need printing from a PC that you happen to be working on the PC that is Connected to the printer ?
You may have heard a lot about the advantages of using the internet for sending e-mail, and decided that you want to get connected .
Or perhaps you are already connected to the internet through a single PC/Modem , but want all of your office colleagues to have access .
All of these situations can be made easier by allowing the various machines to communicate with each other ? by networking the PCs but sometime you don?t know that your PC has (NFS) operating system for sharing file systems and directories across TCP/IP – based Networks.
Network File System (NFS) is a popular network operating system and it?s a distributed file system that allows users to access files and directories located on remote Computers and treat those files and directories as if they were local. For example, users can use operating system commands to create, remove, read write and set files attributes for remotes files and directories.
NFS was first introduced by Sun Microsystems in the early 1980s and was quickly adopted as de facto standard for sharing files and printers between UNIX system. This standard was extended to include PCs and became the basis for must transparent file and print connectivity software solutions . Examples of using NFS
Creating a /usr/local environment in a multi architecture environment. Some directories such as man and doc are architecture neutral, others such as bin and lib are architecture specific.
Creating a rational user file system, when users have files located on their specific machines NFS can be used to make it look coherent on the server.
Creating a central mail spool for all users. This allows users to sign on any machine and access there mail.
In this report , I highlighted some inquires that related with NFS such as :
? Sun Microsystems provides NFS version 4
The NFS standard, which Sun created and turned over to the Internet Engineering Task Force (IETF), enables diverse operating environments to access and share remote files across the network. NFSv4 improves on four areas of the standard: security, performance, interoperability and Internet access. To provide strong security for NFS v4, implementations of the protocol must provide for the use of Kerberos V5 and Public Key Infrastructures through the use of the Low Infrastructure Public Key, LIPKEY; dynamic client response to changes on NFS servers; namespaces that are compatible across all platforms; client file caching that provides for good performance via the Internet while maintaining performance in the traditional LAN environment; and compound operations to minimize the number of connections necessary per transfer.
? The relationship between NFS server and Client file system.
NFS consists of the NFS server and the NFS client software. The NFS server is implemented as a daemon, waiting for requests from clients. The NFS server does not retain the state of the NFS client.
? Architecture of NFS.
NFS is designed to give users high performance, transparent access to server file systems on global networks. Some of the most important design principles are summarized below:
Transparent Access, Statelessness, Portability, Fast Recovery From Failure, Network Protocol Independence, Performance, Security.
? Are there any Alternative for NFS?
Other alternatives to NFS include:
- AFS — Andrew File System developed at CMU
- DFS — Distributed File System from OSF.
- RFS — Remote File System found on older V.3 versions
ofUnix.
- Netware — Novell based file system.
- CIFS — Common Internet File System
? What is CIFS (SMP) ?
CIFS defines a standard remote file system access protocol for use over the Internet, enabling groups of users to work together and share documents across the Internet or within their corporate intranets. CIFS is an open, cross-platform technology based on the native file-sharing protocols built into Microsoft? Windows? and other popular PC operating systems, and supported on dozens of other platforms, including UNIX?. With CIFS, millions of computer users can open and share remote files on the Internet without having to install new software or change the way they work.
? Technology comparison between NFS and CIFS(SMP).
In every textbook description of NFS, its statelessness is emphasized. NFS operations are idempotent (can be repeatedly applied harmlessly), or if non-idempotent (e.x., file deletion) are managed safely by the server. Clients are oblivious to server reboots (if service is restored promptly), with few exceptions. The NFS protocol emphasizes error recovery over file locking ? error recovery is simple if no state need be preserved.
A CIFS file server is not stateless. The CIFS protocol emphasizes locking over error recovery because PC application software relies on strict locking. Strict locking requires a sustained connection. It is imperative that an active session not be interrupted. Applications executing on PC clients react to a CIFS server in exactly the same manner as they do to local disk drives: a down server is no different a condition than an unresponsive disk drive. Therefore, PC clients must be warned — and allowed time — to gracefully disengage (i.e., save files, exit applications, and so on) before server shutdowns or reboots.
I have explaned similarly points between NFS and CIFS ,which to be provided in the conclusion last report .
1.1 Sun Microsystems provides NFS version 4
When the NFS protocol was designed, machines were far less powerful than today, networks were more commonly local area networks (LANs) than wide area networks (WANs), and available security mechanisms were relatively easy to exploit. Additionally, although NFS was designed to interoperate between different operating systems, many of the protocol features have favored UNIX ? file semantics. This history has led to problems in using NFS solutions over the Internet, where security, performance, and interoperability are key. Version 4 of NFS is designed to address these concerns by providing:
? Improved access and good performance on the Internet
? Strong security, with security negotiation built into the protocol
? Enhanced cross-platform interoperability
? Extensibility of the protocol
Stronger in its support of intranets and the Internet, NFS Version 4 will also provide excellent service in environments currently standardized on earlier versions of NFS. Unlike versions 2 or 3, NFS Version 4 can be an important element in the strategy of enterprises to provide better support for global networks.
Although NFS Version 4 owes its general design to previous versions of NFS, it is a self-contained protocol that does not have any dependencies on the previous versions. However, to address backward compatibility with the installed base, Versions 2, 3, and 4 can be supported concurrently. Current users of NFS Versions 2 and 3 may look forward to NFS Version 4 as a reasonable, solid migration strategy to serve their Internet and intranet distributed file system needs.
At the time of the publication of this white paper, the NFS Version 4 protocol is still under development by the IETF(1), so, the final standard may not incorporate all of the features exactly as they are described here.
However, NFS Version 4 uses a universal character set, so it doesn?t matter if the user accessing the file has a different locale than the user who created the file. This universal programming of the character makes it possible to determine what language the character is from and how to display it on the client. The server does not need to associate a locale with a pathname.
IETF(1) the IETF is an open international community with evolution of the internet architecture .As such ,it is the principal body engaged in the development of anew internet standards and procedures.
2.1 The relation between the NFS server
and Client file systems
NFS consists of the NFS server and the NFS client software. The NFS server is implemented as a daemon, waiting for requests from clients. The NFS server does not retain the state of the NFS client.
The NFS server daemon is multithreaded; it processes multiple NFS client calls, in parallel. The NFS server daemon is also an event-driven, asynchronous process. Each NFS client call contains all the information necessary to complete the request see Figure ( 1 ) .
The NFS client software implements a state mechanism that maintains all information required for processing client requests. Each client operation can be requested more than once and contains all the information necessary to complete the request. This model presumes no file open and close requests because these require saving the state of the object and that the server write data to the disk before returning the reply message to the user.
When mounting a remote file system, an NFS client sends a message that makes the remote file system part of the local file directory. The remote host redirects operations that access files on the remote file system to the NFS client software. The NFS client and NFS server then exchange messages.
Figure 1 The division of NFS between client and server
NFS Follows the Client ?server model, in which the server is the system that owns the file system resource and is configured to share it with other systems .An NFS-shareable resource is usually referred to as an exported file system. The client is the resource user .It uses the exported file system as if it were part of the local file system .To achieve this transparency, the client is said to mount the exported directory to the local file system.
In Figure(2) , /efs is the exported directory on host netrix (the NFS server). To access that directory from client jade, it must be mounted first.
To do that ,the administrator creates the /ifs directory to use as the mount directory and issues the appropriate mount command .
Consecuently, to access the file budget.rpt from host jade, the user must specify /ifs/reports/budget.rpt as the path to that file.
Figure 2 The relationship between the NFS server and client file systems.
To transparently access the file budget.rpt from host jade, the user mounts the exported directory /efs on NFS server netrix and specifies / ifs/report/budget.rpt as the path to the command.
3.1 Architecture of NFS
NFS is designed to give users high performance, transparent access to server file systems on global networks. Some of the most important design principles are summarized below:
Transparent Access: Users and applications can access remote files as if they were local. They are not required to know whether the files reside on the local disk or on remote servers.
Portability: NFS is machine and operating system independent. This allows it to be ported easily to multiple OS and hardware platforms from PCs to mainframes.
Fast Recovery From Failure: NFS is designed to recover quickly from system failures and network problems, causing minimal disruption of service to users.
Network Protocol Independence: NFS has the flexibility to run on multiple transport protocols instead of being restricted to just one. This allows it to utilize existing protocols today as well as new protocols in the future.
Performance: NFS is designed for high performance so that users can access remote files as quickly as they can access local files.
Security: The NFS architecture enables the utilization of multiple security mechanisms. This allows system administrators to choose the security mechanism that is appropriate for their distributed file sharing environment instead of being restricted to one solution. This also allows NFS to utilize new security mechanisms in the future.
These features are implemented within the NFS client/server framework which reduces costs by enabling heterogeneous resource sharing across the global enterprise. Servers make their file systems sharable through a process called exporting. Clients gain access to these file systems by adding them to their local file “tree” via the mount process. The NFS protocol provides the medium for communication between client and server processes over the network.
1.2 Alternative for NFS
Naturally ,as a mechanism ,NFS has competitors .In particular ,integration of MS_DOS systems with file servers will certainly not be achieved by equipping all PCs with PC-NFS . For examples Remote File System (RFS), Open Software Foundation?s Distributed Computing Environment includes the Distributed File System (OSF/DCE DFS ).
There are two primary methods currently used to provide PC to UNIX connectivity. The first, based on use of the Network File System (NFS) has been widely implemented since the early 1980?s. The second, newer alternative is based on using the Common Internet File System (CIFS), formerly known as SMB (Server Message Block).
SMB is an important protocol because of the large number of PCs out there that already have client and server implementations running on them. All Windows for Workgroups, Windows 95 and Windows NT systems are (or are capable of) running SMB as either a client, a server, or both.
2.2 What is CIFS (SMP)?
SMB, which stands for Server Message Block, is a protocol for sharing files, printers, serial ports, and communications abstractions such as named pipes and mail slots between computers as Figure ( 3 ) .
Figure ( 3 )
The earliest document I have on the SMB protocol is an IBM document from 1985. It is a copy of an IBM Personal Computer Seminar Proceedings from May 1985. It contains the IBM PC Network SMB Protocol. The next document I have access to is a Microsoft/Intel document called Microsoft Networks/OpenNET-FILE SHARING PROOL from 1987
3.2 SMB Clients and Servers Currently Available
There are a few SMB clients available today and a relatively large number of servers available from a range of vendors. The main clients are from Microsoft, and are included in Windows for WorkGroups 3.x, Windows 95, and Windows NT. They are most evident when you use the File Manager or the Windows 95 Explorer, as these allow you to connect to servers across the network. However they are also used when you open files using a UNC (universal naming convention).
Some other clients that I am aware of are:
? smbclient from Samba
? smbfs for Linux
? SMBlib (an SMB client library that is in development)
Server implementations are available from many sources. Some that I am aware of are:
? Samba
? Microsoft Windows for Workgroups 3.x
? Microsoft Windows 95
? Microsoft Windows NT
? The PATHWORKS family of servers from Digital
? LAN Manager for OS/2, SCO, etc
? VisionFS from SCO
? TotalNET Advanced Server from Syntax
? Advanced Server for UNIX from AT&T (NCR?)
? LAN Server for OS/2 from IBM
There are four basic things that one can do with Samba:
1. Share a Linux drive with Windows machines.
2. Access an SMB share with Linux machines.
3. Share a Linux printer with Windows machines.
4. Share a Windows printer with Linux machines.
4.2 Comparison between NFS and CIFS(SMP)
Here is how they compare from a user?s perspective.
NFS CIFS (SMB)
1 Background NFS was first introduced by Sun Microsystems in the early 1980s and was quickly adopted as the de facto standard for sharing files and printers between UNIX systems. This standard was extended to include PCs and became the basis for most transparent file and print connectivity software solutions. SMB was introduced as a PC networking standard by Microsoft in the early 1980s. It is the Microsoft native method of allowing file and print sharing among network users. Modern connectivity solutions have extended CIFS capabilities to allow UNIX systems to function as CIFS servers.
NFS CIFS (SMB)
2 Connectivity Model The NFS approach allows PCs to work within a UNIX-oriented network by adding NFS client technology to PCs. This “Windows Way” approach of CIFS allows UNIX to function as a native Windows server. This means that UNIX resources simply show up in the existing PC network.
3 Connectivity Model (continued) The NFS model requires that NFS client software be loaded on each PC on the network. A CIFS software server is simply added to any UNIX server on the network. No additional software needs to be loaded on the PCs to get transparent file and print services.