And while on the subject of official Virtual Server 2005 R2 information starting to becoming public, we now support iSCSI for VHD storage and clustering shared storage. Typically iSCSI can be a far cheaper alternative to fibre channel attached storage, and can perform very well. To find out how you can use iSCSI with Virtual Server 2005 R2, again, hot off the press, here's the link to a document on microsoft.com.
Note that to implement an iSCSI solution, you should be looking using Gigabit ethernet minimum for connectivity from host to device. You will need the iSCSI initiator software which you can download for free here, and either a hardware or software solution. Hardware solutions will be more expensive, but there are some excellent software solutions out there as well including WinTarget from Stringbean Software.