While at TechEd IT Pro North America 2008, I also had the opportunity to attend Brent Alinger's session on Exchange Server 2007 and Hyper-V.  Brent is a Senior Test Lead on the Exchange Team at Microsoft, and he's leading our testing efforts around Hyper-V.

Brent described a number of terms, such as the Hyper-V root (which is the parent or the host machine), Hyper-V guest (which is the child or virtual machine), virtual hard disks (VHD), passthrough disks, fixed and dynamic disks, and virtual machine state files.  Some of the more noteworthy bits of info from the session are:

• Within 60 days of Hyper-V's RTM, the Exchange team will publish a detailed support statement for Hyper-V, and a TechNet article with best practices. I'm part of the Exchange Virtualization Working Group and will be helping to deliver some of this content.
• Customers should not deploy Exchange on Hyper-V until our support guidance is available.
• Early results show that performance of Exchange 2007 on Hyper-V is quite good, and that it scales very well from 1-4 processors per VM.

In terms of best practices and requirements, Brent shared the following:

• We're only supporting guests running Exchange Server 2007 SP1 on Windows Server 2008.
• We're only supporting fixed disks, and not dynamic disks.
• Storage should be on spindles that are separate from the Guest operating system VHD physical storage.
• Storage must be SCSI passthrough or iSCSI (with a preference of SCSI passthrough for queues, databases and log files).
• All Exchange server roles, except for the Unified Messaging server role, will be supported.
• There's a limit on VHD size of 2040 GB.

Brent also mentioned that Hyper-V is a good fit when Exchange servers in branch offices cannot be consolidated to a central datacenter (for example, because of bandwidth or connectivity issues).

In terms of workload, not every workload is a candidate for virtualization.  For example, server roles such as Client Access and Hub Transport can be good candidates, but a more heavy hitter like the Mailbox role (which often uses all available resources on a physical server) might not be the best candidate for virtualizing.

It was a great session, and you can expect to hear a lot more about Exchange 2007 and Hyper-V over the coming months.