Virtualization enables the separation of an operating system and the physical device, the chips that it runs on. An imperfect but close enough metaphor is auto rental. Rather than purchasing a car, that may be too big for many tasks and too small for others, a user can rent just the right size car or hail a car-sharing company. Virtualization reduces overall computing costs.


In virtualization, one CPU/RAM/disk stack may run multiple operating systems concurrently, with each separated from the others. In another example, multiple CPU’s are tied together and virtualized as one seemingly enormous computer.

Separating the computer from the operating system enables end-users to rent only the computing power they need for a given task lowering overall costs. It also enables the fast cloning of extra computers.

For example, if a class needs 30 identical computers for 30 students for an exercise, they could use 30 virtual machines with students using only physical screens and other input/output equipment. After completion, the push of a button deletes 30 computers. The school pays only for the time used.

Similarly, if a researcher needs one enormous computer for a large data project they could rent one for the time required that consists, somewhere, of many CPU’s tied together. This is far less costly than purchasing the machine and leaving it idle.

Most virtual input/output devices connect to the physical machines via the web. However, some applications, especially banking or the military, might use private networks. For example, a bank might offer employees virtualized computers where the physical machine isn’t much more than a screen and keyboard. This saves space, a premium on the trading floors of investment banks, and is also more secure.


Virtualization is similar to the large centralized “timeshare” computers dating back to the 1960s. Those were rented on an as-needed basis by businesses who did not want to purchase or maintain the large, expensive, and finicky machines. However, the ability to string together multiple parts of a computer, not just one big central computer itself, make virtualization different. Virtualization is key to “the cloud” – a computer that exists only “in the ether.”

Husband/wife team Diane Greene and Mendel Rosenblum co-founded VMWare, the inventor of virtualization.