Using iSCSI to enable shared storage between virtual machines in Windows Server
2008 R2 was the only option and was also the only way to access volumes greater than
2TB (when not connecting to a Windows iSCSI target, which still had a 2TB limit
because it used VHD as the storage) without using a pass-through disk. If iSCSI is the
storage standard for your organization, using it within virtual machines is still a
workable solution. With Windows Server 2012 R2 and above, though, there is a better
option, which I go into in the section “Leveraging Shared VHDX and VHD Sets.” A
benefit of iSCSI is that the Hyper-V host itself does not require any access to the
storage. The virtual machine’s guest OS IQN is what is given permission to the target
and not the host.
There are also some challenges that you should be aware of when using iSCSI:
Hyper-V has no knowledge that the virtual machine is using iSCSI-connected
storage.
If a backup is taken of the virtual machine at the Hyper-V host, none of the data
stored in iSCSI targets would be backed up.
While technologies like Live Migration and Hyper-V Replica (only if the VSS
integration component is disabled for the VM) will still function, they protect and
move only the VHDX/VHD content and not data stored on iSCSI targets.
To use iSCSI, the guest operating system must know details of the iSCSI fabric,
which may not be desirable, especially in hoster scenarios.