Slow nfs upload - how to speed ?

When I directly copy a file over SSH, I get 11Mb/s speed. But NFS backup is not that fast. Actually too slower.

I changed nfs mount in storage.cfg
options vers=3,rw,rsize=8096,wsize=8096

but does not seems to helped. Is there something I am missing? I am using nfs share to store vzdumps but it is slow.