Comparison and Analysis of features of each NFS Version

NFS is a network file system. With the continuous development of the network, the Protocol version is also increasing. Now we have the latest version 4.1. Are you confused about the version information? It doesn't matter. Here we will explain the content of the NFS version.

1. NFS-Network File System

2. Launched by Sun Microsystems in 1985

3. A common File Sharing Solution

4. linux supports NFS Version 2 from the 1.2 series kernel and NFS Version 3 after the 2.2.18 kernel (I recently used the 2.14.3 kernel and found that NFS Version 4 is supported)

The NFS protocol has been available in multiple versions since its birth, such as NFS V2rfc1094) and NFS V3rfc1813) the latest version is V4rfc3010)

5. NFS Version 3 is faster than NFS Version 2. Version 3 software must be able to implement interoperability with version 2.

6. Differences between V3 and V2:

1> File Size

V2 supports up to 32-bit file sizes (4 GB), while NFS V3 supports 64-bit file sizes.

2> File Transfer size

V3 does not have a limited transmission size. V2 can only be set to 8 KB at most. You can use-rsize and-wsize to set it.

3> return complete information

V3 has added and improved the return of many errors and successful information, which brings great benefits to server settings and management.

4> added support for TCP transmission protocol

V2 only provides support for the UDP protocol, which has great limitations in some demanding network environments. V3 has added support for the TCP protocol.

5> asynchronous writing

Introduction to asynchronous write feature v3:

Whether NFS Version 3 can be written asynchronously is an optional feature. the NFS V3 client sends an asynchronous write request to the server. before replying to the client, the server does not have to write data to the memory stably ). the server can determine when to write data or aggregate and process multiple write requests, and then write data. the client can maintain a copy of the data, in case the server cannot completely write the data. when the client wants to release this copy, it will pass this operation process to the server to ensure that each operation step is complete. asynchronous writing allows the server to determine the best data synchronization policy. how can data be submitted synchronously as much as possible. compared with V2, this mechanism can better achieve data buffering and more parallel balances ). the NFS V2 SERVER cannot write data to the memory before writing data.

6> improved SERVER mount Performance

7> better I/O WRITES performance.

9> enhanced network operation efficiency, making network operation more effective.

10> better disaster recovery functions.

7. Improvement of V4 over V3:

1> improved INTERNET access and execution efficiency

2> enhanced security features in protocols

3> enhanced cross-platform features

8. NFS runs on Sun's RPC protocol. Therefore, UDP can be used and TCP can be used as the lower-layer transmission protocol. However, TCP has more advantages. The client determines whether to choose TCP or UDP.

Most NFS servers in linux do not support TCP transmission.

9. Locking NFS files is a tough issue. NFS servers are stateless and they do not know which machine is using a specific file.

10. The rquotad disk quota method is outdated.

11. cookies and stateless Installation

12. Naming rules for shared file systems: it is best to provide a deep structure such as/home/share1 to ensure that the root directory of the client is not chaotic.

13. Security: prohibit access to TCP and UDP 2049 ports used by NFS

Blocks portmap listening for TCP and UDP ports 111.) daemon access

14. Name of the NFS server startup script

RedHat/etc/init. d/nfs

SuSE/etc/init. d/nfsserver

Debian/etc/init. d/nfs-kernel-server/etc/init. d/nfs-common

15. The mountd service is used for installation requests.

Nfsd is a daemon for running NFS. If the client wants to export its own file system, it must also run nfsd)

View the average load through uptime and adjust the number of nfsd threads

Performance problems caused by checking the number of nfsd threads through nfsstat

Monitor the number of UDP interface overflow through netstat-s, increase the number of nsfd threads to reduce the number of overflow to 0, and add a few more

You can edit the startup script to change the number of nfsd processes.

16. The client's file system installation and file access processes are completely different. Different daemon processes provide services using different protocols:

Nfsd (or rpc. nfsd) is used for file services.

Mountd (or rpc. mountd) is used for the installation request

Portmap uses SUN's RPC protocol