Have you ever tried managing a Windows Server 2008 R2 Hyper-V host using System Center Virtual Machine Manager 2008 (the RTM version, not the R2 version) but kept running into issues that prevented it from working properly? If so then today's tip is for you:
The original version of VMM 2008 doesn’t support managing Windows Server 2008 R2 Hyper-V hosts. To manage Windows Server 2008 R2 Hyper-V hosts, you'll need to upgrade to System Center Virtual Machine Manager 2008 R2.
To make it even more official, the following TechNet site has been updated to state that managing Hyper-V R2 hosts requires VMM 2008 R2: http://technet.microsoft.com/en-us/library/cc764213.aspx.
Hope this helps,
J.C. Hornbeck | System Center Knowledge Engineer