How to boot a VM in Hyper-V from iSCSI

Hyper-V virtual machines do not emulate an iSCSI HBA or allow you to pass a physical iSCSI HBA through to the virtual machine. However, as Hyper-V supports booting virtual machines directly off of physical hard disks, you can attach an iSCSI LUN to the parent partition and then boot the virtual machine off of it.
In order to do this you would need to:

1. Attach the iSCSI LUN to the parent partition.
2. Create a new virtual machine and opt to configure the hard disk later.
3. Open the settings for the new virtual machine and select the first IDE controller.
4. Select to add a disk drive.
5. On the disk drive configuration page select to use a physical hard disk, and select the iSCSI LUN.
6. Apply changes and close the virtual machine settings.

Now you can boot the virtual machine directly off the iSCSI LUN by just starting it up...

Reference: http://blogs.msdn.com/virtual_pc_guy/archive/2008/02/19/booting-hyper-v-vms-off-of-iscsi.aspx