CentOS 5 Server :: Nfs Hard - Intr - Not Enough ?

I'm trying to implement a backup server which must export the /home as follows: /home *(rw,no_root_squash,no_subtree_check,async)

And the client mount it in this way:

My problem is the interruption of network ... in the sense that if the client or the backup server loose network connection no longer stops the transfer, but also freezes all the client has mounted the backup server. ..

How can I be able to give the error signal to the command that is writing in nfs since it is a batch process?