I’ve seen a number of threads and questions recently around iSCSI performance in virtual machines.  If you are looking for Hyper-V information I suggest you check out the following paper:

iSCSI 10 Gigabit Ethernet Performance Tuning With Windows Server® 2008, Hyper-v and the NetApp FAS® 3070

http://download.microsoft.com/download/F/B/3/FB38CA2C-6694-4D25-8452-4A28668A87F2/MSFT-NetApp-10G.docx

This paper has a really good overview of storage solutions and performance comparison graphs.

Enjoy,

    Tony