A must read blog for all Exchange gurus!
In 2005, we set out developing Exchange 2007. During the preliminary planning of Exchange 2007, we realized that the server architecture model had to evolve to deal with hardware constraints, like CPU, that existed at the time and would exist for a good portion of the lifecycle of the product. The architectural change resulted in five server roles, three of which were core to the product:
Read the complete blog at http://blogs.technet.com/b/exchange/archive/2013/01/23/exchange-2013-server-role-architecture.aspx
Read my favorites blogs:
Designing a backup less Exchange 2010 Architecture
Step by step guide for upgrading Active Directory from Microsoft Windows 2003 to Microsoft Windows Server 2008
Microsoft Exchange 2010 CAS Array – Steps and Recommendations
Appear Offline in Microsoft Office Communicator Server 2007
Microsoft Exchange 2010 Test cases
Microsoft Exchange Server 2010 Disaster Recovery
Microsoft Exchange Server 2010 Upgrade Guide