Mainframes, PCs, networks, and the Internet all drastically changed the computer industry. Virtualization based on the x86 platform is another industry reshaper, but what exactly is it?

Your standalone PC comprises hardware and software. You have a CPU, memory, and disk resources. A single operating system sits on top of your hardware resources and controls access to them. On top of your operating system sit applications such as e-mail and word processing. To access the hardware, your applications ask the operating system to perform hardware actions on their behalf. Say you want to save a Word file, like this chapter: You click the Save button, and the word processor says to the operating system, "Please write this data to the hard disk and let me know when you are done."

The operating system takes the data and calls the disk hardware drivers to write the data to the disk drive. The drivers write the data and tell the operating system that they're done. Then the operating system tells the word processor that the data has been written to disk. Suddenly, after a few breathless seconds, you happily see that your document has been saved without error.

While you continue writing, your computer has very little to do. In fact, it's just sitting there waiting for you to type your next character. To understand the wait, you need to understand Hertz (Hz). One Hz is one cycle of something every second. The second hand on a clock moves at a speed one tick a second. Each movement is ...

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