How Hardware Virtualization Works

Hardware virtualization is a rapidly growing practice among small and medium-sized businesses (SMBs). That's because business owners and managers are discovering the great benefits and cost savings hardware virtualization can provide.

For example, virtualization allows you to run multiple "virtual machines" on a single computer, instead of needing to have a separate physical machine for each workload. That saves your business money by reducing the number of computers you have to purchase and maintain to run all your applications and service all your users.

But how does hardware virtualization actually work? Here's a brief explanation.

Normally each physical server consists of the computer hardware (often referred to as "bare metal"), along with operating system (OS) software, such as Windows or Linux. Your application programs, like Microsoft Word or Excel, run on top of the OS. When the application needs a service, such as access to a disk file, it asks the OS to provide it. So, the OS is the intermediary between the application programs and the bare metal.

In this traditional environment, the operating system controls both the hardware and the application programs. For that reason, there can only be one OS running on a physical server at a time.

But by using hardware virtualization, multiple operating systems can run on a single physical machine. Here's how.

In a virtualized environment an additional layer of software, called a hypervisor, is inserted between the bare metal and the operating system(s). When an OS thinks it's interacting with the hardware in order to access a disk file that one of its applications needs, in reality, it's talking to the hypervisor. In fact, each OS on the machine thinks it's the only one because the hypervisor interacts with it exactly as the bare metal hardware would. The OS literally can't tell the difference.

The result is that the hypervisor can service several different operating systems, each with its own set of applications. And none of those operating systems is aware of the existence or the activities of the others. The hypervisor keeps them entirely separate from one another.

So, it's the hypervisor, always a very small and speedy piece of software, that unleashes the magic of hardware virtualization.

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