Information Technology Reference
In-Depth Information
computers. Grid technology, therefore, can be thought of as the technology that enables the
establishment of network-distributed parallel processing and distributed and large-scale
cluster computing.
Both virtualization and grid computing technologies have become two fundamental
building blocs of cloud computing.
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LOUD
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OMPUTING
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D
EFINITION
A Web search for cloud computing is likely to reveal a stream of definitions. There seems
to be no common standard or definition for cloud computing (Voas and Zhang, 2009;
Grossman, 2009). A study conducted by McKinsey (the global management consulting firm)
found 22 definitions for cloud computing. A more commonly used definition describes it as
clusters of distributed computers (largely vast data centers and server farms) which provide
on-demand resources and services over a networked medium (usually the Internet). The term
“cloud” was probably inspired by cloud illustrations depicting the Internet which are often
found in many computing textbooks and journals.
In order to understand what cloud computing is all about it is perhaps useful to have an
idea of the type of services it offers for consumers. The following is a list of the three main
types of services offered by cloud computing (Sultan, 2009):
•
Infrastructure as a Service (IaaS): Products offered via this mode include the
remote delivery (through the Internet) of a full computer infrastructure (e.g.,
virtual computers, servers, storage devices etc.);
•
Platform as a Service (PaaS): To understand this cloud computing layer, one
needs to remember the traditional computing model where each application
managed locally required hardware, an operating system, a database,
middleware, Web servers, and other software. One also needs to remember the
team of network, database and system management experts that are needed to
keep everything up and running. With cloud computing, these services are now
provided remotely by cloud providers under this layer;
•
Software as a Service (Saas): Under this layer, applications are delivered through
the medium of the Internet as a service. Instead of installing and maintaining
software, you simply access it via the Internet, freeing yourself from complex
software and hardware management. This type of cloud service offers a complete
application functionality that ranges from productivity (e.g., office-type)
applications to programs such as those for Customer Relationship Management
(CRM) or Enterprise Resource Management (ERM).
Despite the flexibility of cloud computing, it should not be assumed that cloud products
offered by any of the above services are likely to work out-of-the-box (i.e., they are not
purely plug-and-play). In some cases they might. Messaging and collaboration cloud products
such as Google Apps are perhaps examples of those out-of-the-box products, even though
they still require some level of configuration nevertheless. Some degree of development (i.e.,
