Virtual Machines in the Data Center

Virtualization

Virtualization promised developers a common hardware appearance across the bewildering array of physical configurations in the data center. It promised data center managers that it would rein in “server sprawl” and pack all those extra web servers running at 5 percent utilization into a high-density, high-utilization, easily managed whole. Guess which story turned out to be more compelling?

On the down side, performance is much less predictable. Many virtual machines can reside on the same physical hosts. It’s rare to see VMs move from one host to another, because it’s disruptive to the guest. (The “host operating system” is the one that really runs on hardware. It provides the virtualization features. “Guest operating systems” run in the virtual machines).