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The Greening of IT
244 How Companies Can Make a Difference for the Environment

Conceptual Architecture and Infrastructure for
Cloud Computing

The conceptual architecture behind a cloud computing platform layer
represents a massive network of “cloud servers” interconnected as if in a
grid running in parallel, sometimes using the technique of virtualiza-
tion to maximize computing power per server. A front-end interface
enables a user to select a service from a catalog. This request gets passed
to the system management, which finds the correct resources, and then
calls the provisioning services, which carves out resources in the cloud.
The provisioning service may deploy the requested stack or web applica-
tion as well:

■ User interaction interface: This is how users of the cloud interface
with the cloud to request services.
■ Services catalog: This is the list of services that a user can request.
■ System management: This is the piece that manages the computer
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resources available.
■ Provisioning tool: This tool carves out the systems from the cloud to
deliver on the requested service. It may also deploy the required images.
■ Monitoring and metering: This optional piece tracks the usage of the
cloud so the resources used can be attributed to a certain user.
■ Servers: The servers are managed by the system management tool.
They can be either virtual or real.

The underlying infrastructure for cloud computing can be based on
either virtualization or grid computing or a combination of both. Grid
computing (or the use of a computational grid) is the application of sev-
eral computers to a single problem at the same time—usually to a scien-
tific or technical problem that requires a great number of computer
processing cycles or access to large amounts of data. It is a form of
distributed computing whereby a “super and virtual computer” is
composed of a cluster of networked, loosely-coupled computers, acting
in concert to perform very large tasks. This technology has been applied
to computationally-intensive scientific, mathematical, and academic
problems through volunteer computing, and it is used in commercial