to avoid this is it advisable to make the mount point down one level of root.
# mount NFS_server:/data /datain this case, if the mount point hang,
# ls -al /would take a long time until the NFS mount timed out.
you should do:
# mount NFS_server:/data /new_directory/dataso if the mount point hang, you can still do listing of root.
# ls -al /would work fine just that
# ls -al /new_directorywould fail.