As to adding CIFS, that is a different issue. You'll need to install Samba to get access for CIFS and there are many different variables to consider for performance. One of the most important ones is the number of file handles you have established. Once the number gets above 128, it seems to slow down a bit.
One other thing to keep in mind, although it may not be related, is that the Red Hat Enterprise 4 default security settings are ultra paranoid. That many cause some issues with NFS.
Do you know...
This was first published in April 2006