1.3. OS Changes Under the Hood

Strictly speaking, a book on the Windows Server 2008 R2 operating system would say nothing about Active Directory or DNS or DHCP or file and print services because technically those areall nothing more than applications on the same level as Word or Excel...just stuff that sits atop the platform that is the core operating system. So, let's get purist for a moment and ask, "What's really new in Server 2008 and 2008 R2?" Server 2003's operating system platform was fairly solid, as anyone who's running a 2003 system right now can attest, but 2008 and R2 saw dozens of small changes, most of which work silently in the background and can be safely ignored; however, there are a few big OS changes that admins should know about.

1.3.1. R2 Is 64-Bit Only

It's been coming for quite some time, but starting with Server 2008 R2, it's official: you must have 64-bit hardware to run Server. This isn't a big surprise, particularly when Exchange Server 2007 (Microsoft's email server product) shipped in a 64-bit-only manner. But given that anything fast enough to run 2008 can run 2008 R2, it may frustrate a few admins who didn't know that R2 was coming so fast and so decided to save a couple of bucks and buy 32-bit hardware for their 2008 servers, only to see R2's new features and wish that they could just upgrade their 2008 boxes to R2 boxes.