How many frontend servers / applicative servers / query server would I need ?
Some tools exist :HP Sizer for Microsoft SharePoint 2010
Screenshots :It is really easy to understand how to use the software, here some screenshots, :
Your first configure the project and the company type,
Configure the number of users for your SharePoint farm and user requests
Which features will they use the most ?
Which storage ?
And click on finish to see the magic appearing :
It even propose the CPU Type AMD :
Cherry on the cake : the price
Do you know any other tool, to help you to size SharePoint Farm ?