The following are a few rough formulas based on a medium usage profile for figuring how many back-end and front-end servers you need, and how much storage:
For our rough estimates, we are assuming the following:
All clients are Web clients.
Therefore, the only inputs to be used are: total number of users, and percent concurrency.
The average size calendar event size is 2K.
Each person creates five events or todos per week.
80% CPU utilization.
900 MHz CPU's
1 GB RAM per CPU
Two years' worth of calendar data stored on system.
The formula is:
Number of CPU's = Number of Concurrent Users divided by 4800
The formula is:
Number of CPU's = 4 CPU's per 500,000 configured users
The formula is:
Amount of Storage = 5 emails per week times 52 weeks a year times 2K per email (5*52*2K)
= 520KB per user per year
For the assumed two years of calendar data, 1 MB per user.