NAS devices support multiple file service protocol to handle file I/O requests to a remote file system.
Following are common protocol for file sharing: 1.NFS 2.CIFS
NFS is predominantly used in UNIX based operating environments;
CIFS is used in window-based operating environments.These file sharing protocols enable users to share file data across different operating environments & provide a means for users to migrate transparently from one operation system to another.
NFS: (Network file system)
NFS is a client/server protocol for file sharing that is most commonly used on UNIX system.
NFS was orignally based on the connectionless user datagram protocol (UDP).
It uses a machine independent model to represent user data.
It also uses RPC (Remote procedure call) as a method of interprocess communication between two computers.
The NFS protocols provide a set of RPCs to access a remote file system for the following operations: 1.Searching files & directories 2.Opening, reading, writing to, & closing after. 3.Changing file attributes. 4. Modifying file links & directories.
NFS uses the 'mount' protocol to create a connection between client & the remote system to transfer data.
NFS (NFSV3) is a stateless protocol, which means that it does not maintain any kind of table to store information about open files & associated pointers.
Currently three versions of NFS are in use: 1.NFS version 2 (NFSV2) 2.NFS version 3 (NFSV3) 3.NFS Version 4 (NFSV4)
Uses to provide a stateless network connection between a client & a server.
Features such as loching are handled outside the protocol.
The most commonly used version, it uses UDP or ICP & is based on the stateless protocol design.
It includes some new features, such as 64-bit file size, asynchronous writes & additional file attributes to reduce re-fetching.
This version uses TCP & is based on a stateful protocol design.
It offers enhanced security.
CIFS: (Common Interface file System).
CIFS is a client/server application protocol that enables client programs to make requests for file & services on remote computers over TCP/IP.
It is a public or open variation of Server Message Block (SMB) protocol.
CIFS protocol enables remote clients to gain access to files that are on a server.
CIFS enables file sharing with other clients by using special locks.
File names in CIFS are encoded using unicode characters.
CIFS provides following features to ensure data integrity.
It uses file & record loching to prevent users from overwriting the worth of another user on a file or a record.
It runs over TCP.
It supports fault tolerance & can automatically restore connections & reopen files that were open prior to interruption.
The fault tolerance features of CIFS depend on whether an application is written to take advantage of these features.