Lately, it seems as though everyone that I talk to is interested in virtualizing at least some of the servers in their organization. Although Hyper-V does a great job as a virtual server hosting solution, it does have some quirks that you might not expect. In this article, I want to talk about some of these quirks and how to work around them.
The CD or DVD Drive is Inaccessible
One of the first issues that network administrators are likely to run into is that the CD / DVD drive is inaccessible from within a virtual machine. The reason why this happens is that a CD or DVD drive can only be used by one virtual machine at a time. In order to use a CD or a DVD drive from within a virtual machine, an administrator must capture the drive.
An administrator can capture or release a CD or DVD drive from the virtual machine’s Media menu. Simply select the DVD Drive command from the media menu, and then choose either the Capture command or the Uncapture command. The Media | DVD menu also gives you the option of capturing an ISO file (A CD or a DVD image file) and treating that file as though it were a CD or a DVD drive.
A New Virtual Machine Won’t Start
When I was first learning my way around Hyper-V, one of the issues that I would commonly run into was that I would create a new virtual machine, and configure that virtual machine to automatically install Windows from a CD. When I would start the virtual machine though, I would receive a cryptic error about an IDE device being in use by another virtual machine. You can see an example of such an error in Figure A.
Figure A You can’t install a new OS from CD / DVD if the CD / DVD drive is already in use.
This error message is caused by the same issue that I talked about in the previous section. If another virtual machine is making use of the server’s CD / DVD drive, then you will not be able to install an operating system off of a CD / DVD onto a new virtual machine until that CD/ DVD drive is released.
After you finish installing Windows in a virtual machine, it initially appears that Windows is functioning normally in a virtual environment. You may soon notice however, that the virtual machine has no network access. If you open the Device Manager, you may also find that many of the hardware devices are listed as Unknown.
To gain access to your hardware, you must install the Integration Services. By doing so, you will install a set of device drivers for the virtual hardware that will allow you to gain access to the network and to the other virtualized hardware devices. If the virtual server is running Windows Server 2003, then you must install SP2 or higher prior to installing the integration services.
Some Hardware Still Won’t Work
Although Hyper-V does a fairly decent job of allowing virtual machines to access your server’s hardware, odds are that the virtual machines will not be able to access any hardware that is highly specialized. Even some of the more common hardware is not supported in a virtual environment.
Probably the best known example of this is that you cannot access USB devices from a virtual machine. Another common example is that a guest operating system will not be able to boot if the virtual hard drive that acts as the operating system’s system drive is stored on a SCSI drive. Virtual system hard drives can only boot from IDE or SATA drives.
As you can see, there are definitely some quirky aspects to Hyper-V. Even so, Hyper-V seems to be a good virtualization solution as long as the virtual server doesn’t have to access any unsupported hardware.
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