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3.1.3
Comparisons to other IT Concepts
Cloud computing is an on‐going development of technologies and principles,
supplemented by the concept of elasticity. Here we will compare it with grid
computing, outsourcing and Application Service Providing.
when there are no shared has its roots in science where computationally
very high resource demand problems, often with large volumes of data, e.g.
weather forecasts or materials research, are solved by loosely coupled
heterogeneous and geographically distributed IT resources across multiple
institutions. Compared with today's concept of the Cloud, grid computing
lacked centralised control of the resources and simplicity of use.
Outsourcing
designates a process in which the responsibility for providing a
contractually defind service is handed over to an external provider. Typically
based on a contract over years, and sometimes at the start of the contract
period ‘inhouse’ IT department staff are transferred to the outsourcer. This
makes Cloud computing a highly flexible form of outsourcing with the
following possibilities:
Shorter lease terms (hours or months)
Elasticity (needs‐driven adding of resources)
Application Service Providing (ASP
)
originated in the 1990s and refers to
offering software over the Internet where the provider handles the
administration. Software as a Service (SaaS), a Cloud offering, is an
extension of the original ASP idea in many respects:
ASPs offered third party software – SaaS provider mainly sold is own
software
APSs needed a locally installed client – SaaS provider used the client
browser
APSs installed separate instances per user ‐ SaaS provider used multi‐
tenant implementations
Some Cloud services include ASP and SaaS offerings.
3.1.4
General Deployment models
At an very early stage Cloud computing was categorised into two typical
manifestations that share specific properties or characteristics. To be more
precise, what is meant here is the classification into “Private Cloud” and
