Looking for pointers

We are about to put into effect a very large proxy/cashe server. This one will
not be just for one campus, but for all campuses in the country (no joke and 
this is not being sent on the 1st).

I am looking for anyone that may have some expertice with handling a very large
area. At this time, I do know that I will have 7 to 8Gb of disk space for cashe.
I may have to cut it down just a little, a Gig or so, for the local non 
proxy/cashe server.

The only thing that we have not picked as of this time, is the machine and op
for it. We will be running the Cern V3.0 server. 

Looking for any ideas or pit falls. No pointers to the warning.gif please.