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providers as Sun and IBM, at the same time there is an evolution in the software
industry towards SaaS pushed by software vendors as for example Microsoft and
SAP. Both developments - Utility Computing and SaaS - illustrate the increasing
trend towards external deployment and sourcing of computing and applications.
What is the next step in the evolution of computing as a service (see fig. 3.9)?
Grid Computing
Utility Computing
Software as a Service
Cloud Computing
Solving large problems
with parallel computing
Offering computing
resources as metered
services
Network-based
subscriptions to
applications
Next-generation Internet
computing
Made mainstream by
Globus Alliance
Next-generation data
centres
Made mainstream by
Globus Alliance
Gained momentum in
2001
Late 1980s
Late 1990
Fig. 3.9:
The Evolution to Cloud Computing (adapted from IBM 2009)
Utility computing and SaaS are two complementary trends: utility computing can
only be successful on the market if a critical mass of applications is able to run on it.
SaaS needs a flexible, scalable and easily accessible infrastructure on which it can
run. Thus, in order to meet market demand, the next natural step in evolution is the
integration of these two trends into a new holistic approach that offers the following
functionality:
• Scalable, flexible, robust and reliably physical infrastructure
• Platform services that enable programming access to physical infrastructure
through abstract interfaces
• SaaS developed, deployed and running on a flexible and scalable physical infra-
structure
All this is emerging in new online platforms referred to as Clouds and Cloud
Computing. Cloud Computing is resulting from the convergence of Grid Computing,
Utility Computing and SaaS, and essentially represents the increasing trend towards
the external deployment of IT resources, such as computational power, storage or
business applications, and obtaining them as services. It has the potential to disrup-
tively change the X-as-a-Service products and markets and will be explained in
more detail in the next chapter.
