There are 17 possible roles and 42 different features that can be enabled on Windows Server 2008 R2 Enterprise Edition. Hyper-V role is not available for Windows Server 2008 R2 Itanium, Windows Server 2008 R2 Web, or Windows Server 2008 R2 Foundation. Another problem in Windows Server 2008 Hyper-V was the inability to dynamically change the storage on a running VM. Unlike in the physical world where you can easily add or remove Universal Serial Bus (USB), eSATA, or iSCSI drives without shutting down a server, the only way to add or remove VHDs from a VM was to shut the VM down
