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What Is Virtualization

by Wei-Meng Lee
Running Mac OS X on Windows
Virtualization allows you to have multiple "virtual machines," each with its own operating systems running in a sandbox, shielded from each other, all in one physical machine. Each virtual machine shares a common set of hardware, unaware that it is also being used by another virtual machine at the same time.

In This Article:

  1. Why Virtualization?
  2. Microsoft Virtual PC 2004
  3. VMware Workstation 5.0
  4. Microsoft Virtual Server 2005
  5. Performance Tips
  6. Summary

Why Virtualization?

Today, there are quite a number of choices when it comes to choosing an operating system for your computer. In the good old days, the choice was much easier -- either you got MS DOS for your PC, or you got an Apple (or Atari), and so on. Today, you have a few more choices for your PC: Windows XP, Windows Server 2003, Linux, and so on.

For those adventurous folks, you might install a multi-boot loader that lets you choose what OS to load during boot-up time. But that involves some experience and a little bit of skill, and partitioning hard disks is not for the faint-hearted. Moreover, once the operating systems are installed it is not a trivial task to add another one into your multi-boot PC.

The rich folks among you might go for the hardware solution, using a different hard disk for each operating system and swapping the required hard disk during boot time. Of course, this is the ideal solution and helps you avoid the nightmare of messing up the multi-boot loader. However, just like the multi-boot solution, only one operating system can run at a time, and switching from one to another takes some considerable delay.

With virtualization, you can have the best of both worlds. You can install new operating systems as easily as installing a new game on your PC, and you can run more than one operating system at the same time. In this article, I will take you through a tour of some of the popular virtualization software available in the market so that you have a better idea of the strengths of each.

Microsoft Virtual PC 2004

Host operating systems supported:

  • Windows 2000 Professional

  • Windows Server 2003

  • Windows XP Professional

  • Windows XP Tablet PC Edition

  • Mac OS X

Microsoft Virtual PC is virtualization software designed to run on Windows and computers running Mac OS X. Originally from Connectix, Virtual PC was acquired by Microsoft in early 2003 as part of its effort to enable its customers to run their legacy Windows applications as they migrate to newer Windows operating systems. In addition, Virtual PC also allows customers to run different operating systems on the same physical machine without needing to commit to additional hardware. More importantly, Virtual PC allows developers to test their applications on different platforms easily on virtual machines, especially for technologies that are still in the beta stage and that should not be installed on production servers.

Figure 1 shows my host operating system (Windows XP Professional) with two guest operating systems: Windows Server 2003 Standard Edition and Linux Mandrake 8.0. The Virtual PC Console (on the top right corner of the screen) contains a list of virtual machines I have installed on my machine. To view each virtual machine in full-screen mode, select the window and press Alt-Enter.

Figure 1
Figure 1. Two guest operating systems in the host operating system

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