mount -o tcp shadowman.example.com:/misc/export /misc/local
If the NFS mount is specified in /etc/fstab:
server:/usr/local/pub /pub nfs rsize=8192,wsize=8192,timeo=14,intr,tcp
If it is specified in an autofs configuration file:
myproject -rw,soft,intr,rsize=8192,wsize=8192,tcp penguin.example.net:/proj52
Since the default is UDP, if the -o tcp option is not specified, the NFS-exported file system is accessed via UDP.
The advantages of using TCP include the following:
- Improved connection durability, thus less NFS stale file handles messages.
- Performance gain on heavily loaded networks because TCP acknowledges every packet, unlike UDP which only acknowledges completion.
- TCP has better congestion control than UDP (which has none). On a very congested network, UDP packets are the first types of packet that are dropped. Which means if NFS is writing data (in 8K chunks) all of that 8K has to retransmitted. With TCP because of its reliability, one parts of that 8K data is transmitted at a time.
- Error detection. When a tcp connection breaks (due to the server going down) the client stops sending data and starts the reconnection process. With UDP, since its connection-less, the client continue to pound the network with data until server comes up.
The main disadvantage is that there is a very small performance hit due to the overhead associated with the TCP protocol.
Source:https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/3/html/System_Administration_Guide/s1-nfs-mount.html
