Optimal setup to handle large tps

Hi All, I was hoping for some advice from some of you: I have a requirement to deploy Freeradius to handle about 2M customers and of course I need to set up my environment optimally. I am aiming for about 1500 auths or accounting requests per second. 1.) Can Freeradius achieve that? Reading the performance blurb suggests it can? 2.) In order to achieve that, I guess it would be best to split auth and accounting to different servers? Agree? 3.) What is the optimal way to use the users file? As a gdbm/dbm data file or plain text file or something else? 4.) Any other advice would be appreciated! Thanks a lot! Kosie