Page 81 - How Cloud Computing Is Transforming Business and Why You Cant Afford to Be Left Behind

VIRTUALIZATION C HANGES EVERYTHING

of the hardware that it’s running on. Thus Windows, Linux,
and Solaris for x86 all understand what to do when the ac-
counting system says, “Add these two numbers”; they pass the
numbers to the “adder” that is etched into the processor and
return the result to the application.
The role of the operating system changed, however, when

virtualization’s hypervisor appeared on the scene. In 1999,
VMware’s former chief scientist, Mendel Rosenblum, demon-
strated in a product, VMware Workstation, that he had cap-
tured the ability to mimic Intel’s complicated and proprietary
x86 hardware instruction set in software. This had long been
thought to be impossible, or at least so difficult that it wouldn’t
be cost-effective to try. Four years after Workstation came on

the scene, the feat was duplicated in the Computer Labora-
tory at the University of Cambridge in the Xen Project led by
Ian Pratt.
Both of these projects have led to hypervisors—the virtual
machine supervisors—that are capable of telling hardware
what to do based on what an application requires. Without go-
ing deeper into the nuts and bolts of hypervisors, this enables
the hypervisor to displace the operating system. Virtualization
lifts the operating system up a layer and slides the hypervisor in

underneath it. Now the hypervisor takes over the role of talk-
ing to the hardware, leaving the operating system to talk only
to the application and pass its needs down to the hypervisor.
The most immediate result of the operating system’s dis-
placement is that it breaks what had hitherto been the surest
of bonds, that between the business application and a partic-
ular piece of hardware.

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