Friday, November 23, 2012

Hyper-V Q & A with John Savill

Q: Are Windows NT 4 and Windows 2000 guest OSs supported on Windows Server 2012 Hyper-V?
A: Windows NT 4 and Windows 2000 are no longer supported by Microsoft, and so can't be supported on Hyper-V. Windows Server 2012 Hyper-V actually dropped integration service support for Windows 2000, which means it's no longer possible to use synthetic devices (such as network and storage) and there are no services to integrate with Hyper-V.

The net effect is the performance would be poor compared to an OS using synthetic devices, because emulated devices would have to be used. The recommendation would be to run Windows 2000 virtual machines (VMs) on a Windows Server 2008 R2 Hyper-V server, which still has integration service support for Windows 2000.

Another (unsupported) option to try could be taking the integration services from Hyper-V 2008 R2 and installing on the Windows 2000 VM, then running on the Windows Server 2012 Hyper-V. This would give some synthetic device support and some integration with Hyper-V but would be completely unsupported by Microsoft. Longer term recommendation would be to migrate to a newer, supported OS as soon as possible.

For Windows NT 4, there really is no support. The legacy processor compatibility mode that helped NT 4 run on Hyper-V is gone in Windows Server 2012 Hyper-V, and emulated devices would definitely have to be used. However, the performance might meet what you need so this could be worth a try.
Q: When upgrading a Hyper-V host from Windows 2008 R2 to Windows 2012, can I save the state of a running VM and resume it after the upgrade?
A: No, you can't save the state of a running virtual machine (VM). The save state format of Windows Server 2008 R2 is not compatible with Windows Server 2012, in the same way the save state format of Windows 2008 wasn't compatible with Windows Server 2008 R2. 
You should shut down all VMs on a host prior to performing an upgrade of the Hyper-V host. Note that if you have online snapshots of a VM which also uses saved state as part of the snapshot, and then these snapshots will work after the upgrade to Server 2012.

Q: How can I attach USB devices to a Hyper-V virtual machine?
A: There are two scenarios for USB devices to be accessed in a virtual machine (VM):
1.      As part of a user's session on a VM
2.      Always available to the VM; for example, a USB dongle that must be available for a piece of software or service to function
Hyper-V doesn't allow the pass-through of a USB-attached device on a host to a VM. This would break the desired abstraction of the VM from the hardware, and therefore stop VM mobility. However this doesn't mean there are no solutions.
For the first scenario, a USB device available as part of a user's session on a VM, the solution is to use the Remote Desktop Protocol (RDP) capability to pass a locally attached USB device on the user's local device directly through to the remote VM. With Windows Server 2012 and RemoteFX technology, it's possible to redirect almost any USB device over RDP.
The second scenario, a USB device to always be connected to a VM even when a user isn't logged on, requires the use of third-party solutions that enable USB over IP. The solutions work by having a physical server that has all the USB devices connected to it and runs a service that enables the USB devices to be accessed remotely over IP.
The VMs then run a piece of client software that connects to the USB device over IP, and it looks to the VM like a local USB device. The benefit to these types of solutions is the VM can still be moved between hosts without losing connectivity to the USB device. There are many solutions available; among them are two I have seen used by my customers:
These questions are answered by John Savill, from WindowsITPro, Millions Thanks to him.

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