Good NFS configuration for Small Network (NFS Performance Issues)
Solution 1:
It's pretty standard for scp to be quicker than NFS; there's a lot more overhead and things that need doing for a network filesystem than for a simple machine-to-machine transfer.
Solution 2:
NFS should give you about 50% of the underlying disk write performance. If your disk does 100MB/s, then you should be able to do 50MB/s NFS write.
About the mount options : use tcp. udp can give pretty bad results if your network is heavily loaded, or any network device is flaky.