11-05-2012, 01:19 PM
Virtualization for Windows
MSVirtualizationOverviewv1.1.pdf (Size: 1.08 MB / Downloads: 52)
Understanding Virtualization
Virtualization is unquestionably one of the hottest trends in information technology today. This is no accident. While a variety of technologies fall under the virtualization umbrella, all of them are changing the IT world in significant ways.
This overview introduces Microsoft’s virtualization technologies, focusing on three areas: hardware virtualization, presentation virtualization, and application virtualization. Since every technology, virtual or otherwise, must be effectively managed, this discussion also looks at Microsoft’s management products for a virtual world. The goal is to make clear what these offerings do, describe a bit about how they do it, and show how they work together.
Virtualization Technologies
To understand modern virtualization technologies, think first about a system without them. Imagine, for example, an application such as Microsoft Word running on a standalone desktop computer. Figure 1 shows how this looks.
A system without virtualization
The application is installed and runs directly on the operating system, which in turn runs directly on the computer’s hardware. The application’s user interface is presented via a display that’s directly attached to this machine. This simple scenario is familiar to anybody who’s ever used Windows.
But it’s not the only choice. In fact, it’s often not the best choice. Rather than locking these various parts together—the operating system to the hardware, the application to the operating system, and the user interface to the local machine—it’s possible to loosen the direct reliance these parts have on each other.
Doing this means virtualizing aspects of this environment, something that can be done in various ways. The operating system can be decoupled from the physical hardware it runs on using hardware virtualization, for example, while application virtualization allows an analogous decoupling between the operating system and the applications that use it. Similarly, presentation virtualization allows separating an application’s user interface from the physical machine the
application runs on. All of these approaches to virtualization help make the links between components less rigid. This lets hardware and software be used in more diverse ways, and it also makes both easier to change. Given that most IT professionals spend most of their time working with what’s already installed rather than rolling out new deployments, making their world more malleable is a good thing.
Each type of virtualization also brings other benefits specific to the problem it addresses. Understanding what these are requires knowing more about the technologies themselves. Accordingly, the next sections take a closer look at each one.
Hardware Virtualization
For most IT people today, the word “virtualization” conjures up thoughts of running multiple operating systems on a single physical machine. This is hardware virtualization, and while it’s not the only important kind of virtualization, it is unquestionably the most visible today.
The core idea of hardware virtualization is simple: Use software to create a virtual machine (VM) that emulates a physical computer. By providing multiple VMs at once, this approach allows running several operating systems simultaneously on a single physical machine. Figure 2 shows how this looks.