One common reason to call in an Applications Architect is to get them to perform sizing for you. Usually the architect surveys the existing IT deployment and then request information about the planned applications. Many factors contribute to the final recommendation - as depicted below:
You can then go about estimating the server configurations yourself or you can present the above information to the Hardware vendor. Most Hardware vendors request you to fill out the information on a questionnaire that you mail out to them. They then revert back with a sizing proposal within 3-4 days.
