Microsoft has released a spreadsheet for Sizing Exchange 2010 to suit the number of users and business requirements. This will let you know things such as:
- How much memory do I need?
- How many servers?
- What are my storage requirements
and so on...
The sizing tool is an excel spreadsheet that can be downloaded from here:
Microsoft has released a 25 minute video that shows you how to use this spreadsheet and what all the functions do. This is available from:
Another handy link around sizing memory in Exchange 2010 is:
The rule of thumb when sizing an Exchange Server 2010 mailbox server is to start with 2GB of RAM for a server; then add 5MB of RAM for each mailbox that will be homed on it. For example, on a server with 3,000 mailboxes, at least 17GB of RAM would be required (2GB + (3000*.005GB)).