Information Technology Reference
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• Multitenancy and resource pooling that allows combining hetero-
geneous computing resources (e.g., hardware, software, processing
servers and network bandwidth) to serve multiple consumers—such
resources being dynamically assigned.
• Rapid elasticity and scalability that allows functionalities and
resources to be rapidly, elastically, and automatically scaled out or
in, as demand rises or drops.
• Measured provision to automatically control and optimize resource
allocation and to provide a metering capability to determine the
usage for billing purpose, allowing easy monitoring, controlling,
and reporting.
13.3 Cloud Delivery Models
Cloud computing is not a completely new concept for the development and
operation of Web applications. It allows for the most cost-effective develop-
ment of scalable Web portals on highly available and fail-safe infrastructures.
In the cloud computing system, we have to address different fundamentals
like virtualization, scalability, interoperability, quality of service, failover
mechanism, and the cloud deployment models (private, public, hybrid)
within the context of the taxonomy. The taxonomy of cloud includes the dif-
ferent participants involved in the cloud along with the attributes and tech-
nologies that are coupled to address their needs and the different types of
services like XaaS offerings where X is software, hardware, platform, infra-
structure, data, and business (Figures 13.1 and 13.2).
13.3.1 Infrastructure as a Service (IaaS)
The IaaS model is about providing compute and storage resources as a ser-
vice. According to NIST, IaaS is defined as follows:
The capability provided to the consumer is to provision processing, storage, net-
works, and other fundamental computing resources where the consumer is able to
deploy and run arbitrary software, which can include operating systems and applica-
tions. The consumer does not manage or control the underlying cloud infrastructure
but has control over operating systems, storage, deployed applications, and possibly
limited control of select networking components (e.g., host firewalls).
The user of IaaS has single ownership of the alloted hardware infrastruc-
ture and can use it as if it is his or her own machine on a remote network and
has control over the operating system and software on it. IaaS is illustrated in
Figure 13.1. The IaaS provider has control over the actual hardware, and the
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