Page 73 - How Cloud Computing Is Transforming Business and Why You Cant Afford to Be Left Behind

VIRTUALIZATION C HANGES EVERYTHING

the general-purpose cloud data center, such as EC2, because
through virtualization, a cloud service can place many users
on one machine without danger that they will trespass on each
other or see each other’s data. The overseer of the virtual ma-
chines is the hypervisor, a superb automated allocator of re-
sources among competing demands.

One hypervisor sits on each server running several virtual
machines; it understands the division of hardware resources
set up by the human system administrator, who assigns each vir-
tual machine a share of the computer’s random access mem-
ory, central processing unit (CPU) cycles, network bandwidth,
and disk storage. Then it referees the competing demands for
these resources. The computer that is running multiple vir-

tual machines is often referred to as the host. The virtual ma-
chines themselves are often referred to as the guests of the
host. The host will be powered by its own operating system,
such as Linux or Windows Server, but each guest has its own
operating system as well. This all sounds confusing at first, but
it works extremely well. Each virtual machine behaves just like
a physical machine in terms of its ability to run a business ap-
plication, and often there is only a small performance penalty
for running ten applications per server instead of just one.

Virtualization is one of the key technologies that gives the
cloud its elastic quality, so that a user can enlist support from
many servers and, conversely, many users can receive services
from the same server. Intel and AMD are routinely delivering
CPUs, the central brain of the computer, that consist of four
cores. Each core is a full microprocessor in itself; four of them
together occupy one microprocessor socket at the heart of the

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