Hardware and performance

We want to the moodle for 25000 users and want to create a web farm.
What are configuration changes we need to do in the moodle so that it can run on the three tier architecture with web server, file server and database server on three different servers.

we are planing to use the load balancer along with three diffrent web server for start and separate database server and file server for moodle data.

Please suggest what all configuration we need to do to support the 25000 users.