(All in x64 )

Windows Server 2008 R2 Datacenter / 2 TB
Windows Server 2008 R2 Enterprise / 2 TB
Windows Server 2008 R2 for Itanium-Based Systems IA64 / 2 TB
Windows Server 2008 R2 Foundation / 8 GB
Windows Server 2008 R2 Standard / 32 GB
Windows HPC Server 2008 R2 / 128 GB
Windows Web Server 2008 R2 / 32 GB


More on: http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778(v=vs.85).aspx