Software Architecture in Practice, 4th Edition

16

Virtualization

Virtual means never knowing where your next byte is coming from.

—Unknown

In the 1960s, the computing community was frustrated by the problem of sharing resources such as memory, disk, I/O channels, and user input devices on one physical machine among several independent applications. The inability to share resources meant that only one application could be run at a time. Computers at that time cost millions of dollars—real money in those days—and most applications used only a fraction, typically around 10%, of the available resources, so this situation had a significant effect on computing costs.

Virtual machines and, later, containers emerged to deal with sharing. The goal of these virtual machines and containers is to isolate ...