In our last discussion we talked about the differences between type 1 and type 2 hypervisors. I told you that the type 2 hypervisor had some significant drawbacks because of the fact that there are 2 Hardware Abstraction Layers to deal with. Performance will certainly be impacted, and Microsoft does not support infrastructure workloads running in a type 2 hypervisor environment. With all those drawbacks you might be wondering if there is any conceivable situation in which we might actually want to use a type 2 hypervisor. The answer is a resounding YES!
Type 2 hypervisors have played the same key role since their inception. They are the ideal solution to ease the transition from one operating system to another. Connectix began their foray into the virtualization space with the creation of a product called Virtual PC for MAC. The product allowed individuals who were running MAC to run the Virtual PC application on the MAC which in turn allowed the running of the Windows Operating system and its plethora of associated applications on the MAC. Awesome!
Connectix used that principle again when they created Virtual PC for use with the Windows Operating system. Microsoft had just released the Windows XP operating system and there were some hesitations among the IT community to change from what they knew well in Windows 98 to a new operating system. (Sounds eeerily familiar doesn’t it!) Anyway Virtual PC provided an ideal transitionery platform from one Windows operating system to another. The virtual PC app was so good that Microsoft chose (over VMware) to purchase Connectix intellectual property.
Microsoft still makes Virtual PC. It is still a type 2 hypervisor, and still plays the role of easing transitions from Operating system to Operating system. In it’s current rendition it is called “Windows Virtual PC” and anyone who would like to use it can download a copy absolutely free.
When you work with Windows Virtual PC it would be important to note that Windows Virtual PC uses a single file to contain the operating system, applications, and files in any guest operating system running in Windows Virtual PC. This file has a .vhd (virtual hard disk) extension. Each VHD has an associated settings file (.vmc for virtual machine configuration) that defines the amount of RAM allocated to the virtual machine, the location of the virtual hard disk, the network connectivity settings, the name of the virtual machine and several other settings.
Pay careful attention here. Hypervisors always use a manager to control the settings, configurations, and operations of operating systems. This manager is called a Virtual Machine Manager or VMM. The Windows Virtual PC VMM is built in to the Windows Virtual PC application. It allows for a dashboard like view of virtual machines and their settings running on the Windows Virtual PC host.
Windows Virtual PC can run a number of guest operating systems within its VMM. Even non Microsoft operating systems. You can of course install and configure your own operating system to run in Windows Virtual PC, or if you prefer you can load a virtual machine that Microsoft created for you.
Let’s say just for instance that you are interested in making he move to Windows 7. However you are in an environment where some of your applications were written specifically for Windows XP. It would seem that you would be stuck without the opportunity to move to Windows 7. Not to fear. If you purchased a copy of Windows 7 in the Professional, Ultimate, or Enterprise edition you have a built in license to run one additional guest virtual machine running Windows XP to host your legacy applications. This functionality is called Windows XP mode.
Windows XP mode is nothing more than a virtual machine created by Microsoft specifically to run in Windows Virtual PC on a supported version of Windows 7. That’s it. I can hear the wheels turning and the lights coming on.
5…4…3…2….1 and there they are. The questions.
1. So if I have a version of Windows 7 that is NOT Professional, Ultimate, or Enterprise can I still run Windows Virtual PC?
Absolutely! To a point. Windows Virtual PC is not supported on the Home Basic or Starter editions of Windows 7.
2. If Windows XP Mode is just a Virtual Machine running in Windows Virtual PC does that mean I can run other guest operating systems on Windows 7 along with XP mode?
3. Could I run other Windows XP virtual machines of my own making in Windows Virtual PC? Sure.
As you can see there is still a place for the type 2 hypervisor in the modern client operating system environment.
Homework: Download Windows Virtual PC and the XP mode virtual machine. Examine the settings associated with XP mode.