Difference between NFS v2, v3 and v4

S.No	Feature	NFS v2	NFS v3	NFS v4
1	Authentication	AUTH_SYS	AUTH_SYS	Kerberos
2	Parallel NFS	NO	No	Yes
3	State	Stateless	Stateless	Statefull
4	RPC Call Type	Single	Single	Compound
5	Exports			All exports can be mounted together in a directory tree structure as part of a pseudo-filesystem
6	Locking	NLM	NLM	Inbuilt in NFSv4 Protocol

Breif Explanantions

1) Authentication

Kerberos is a computer network authentication protocol that works on the basis of tickets to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner

2) Parallel NFS

That is, when a server implements pNFS, a client is able to access data through multiple servers concurrently. It supports three storage protocols or layouts: files, objects, and blocks.

3) State

A data structure change_info is returned by CREATE, LINK, OPEN, and REMOVE calls so the clients become aware about concurrent operations done on the NFS directories and files by the other clients. Clients can perform efficient caching and discard cache depending on the change_info

4) RPC Call type

This mix of a typical NFS set of RPC calls in versions prior to NFSv4 requires each RPC call is a separate transaction over the wire. NFSv4 avoids the expense of single RPC requests and the attendant latency issues and allows these calls to be bundled together. For instance, a lookup, open, read and close can be sent once over the wire, and the server can execute the entire compound call as a single entity. The effect is to reduce latency considerably for multiple operations.

5) Exports

In NFS v4 Servers, rather than exporting multiple file systems, export a single "pseudo file system," formed from multiple actual file systems, and customized for each client.

6) Locking

NFSv3 relied on Network Lock Manager (NLM) for file locking . NLM was itself a separate protocol, so file locking glued together rather than being a core part of the file access protocol. NFSv4 changes that.

From Client : nfsstat -m