Virtual Machines Change the Boundary

Virtual machines changed the arrangement. A physical server could run a virtualization layer, and that layer could run several virtual machines. Each virtual machine behaved like a separate computer with its own operating system. Different applications could therefore share one physical server while remaining isolated in separate operating-system environments.

The university might run HopPress in one virtual machine and CourseTracker in a second one. The physical server is shared, but the applications do not need to be installed into the same operating-system environment.

Organizations could use their existing hardware more efficiently. They could create a new machine through software instead of buying one. And they could move a virtual machine far more easily than they could move a physical server. The boundary of deployment shifted from a physical machine to a virtual machine.

Virtual machines solved the first problem: one application no longer wasted most of a physical server. But every virtual machine still carries a complete operating system, which consumes memory and storage, needs updates, and must be monitored. If ten applications each require a separate virtual machine, the organization is now operating ten operating-system environments in addition to the applications themselves. The next step was to move the boundary again, this time to the application itself.