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raw compute, storage, and network resources as a pool of resources and building
resource overlays such as data storage services on top of them (Foster et al. 2008).
Encapsulation of applications ultimately improves security, manageability, and
isolation (Foster et al. 2008). Another important feature of Clouds is the integration
of hardware and system software with applications. Both the hardware and systems
software, or infrastructure, and the applications are offered as a service in an inte-
grated manner.
Based on the findings of the definition analysis, a summary of the defining
features of Cloud Computing, as they will be applied to guide further discussions in
this topic, is provided below and in figure 4.1:
• Cloud Computing is a new computing paradigm.
• Infrastructure resources (hardware, storage and system software) and applica-
tions are provided in a X-as-a-Service manner. When these services are offered
by an independent provider or to external customers, Cloud Computing is based
on pay-per-use business models.
• Main features of Clouds are virtualization and dynamic scalability on demand.
• Utility computing and SaaS are provided in an integrated manner, even though
utility computing might be consumed separately.
• Cloud services are consumed either via Web browser or via a defined API.
Access of
Software
as a Service
via web
browser
Access of
Software
as a Service
via API
Software
Cloud Access
Interface
Cloud
User
API
Cloud Access
Interface
API
Abstraction of raw
hardware resources
through
virtualization
Virtualization Layer
Access of
scalable
and
virtualized
infrastructure as a
service via API
(utility computing)
Scalability
Dynamic adjustment
of provisioned IT
resources to variable
load
Data centres of Cloud provider
Fig. 4.1:
Defining features of Cloud Computing
