Cloud computing is the use of computing resources (hardware and
software) that are delivered as a service over anetwork
(typically the Internet). For example, email. The name comes from
the common use of a cloud-shaped symbol as an abstraction for the
complex infrastructure it contains in system diagrams. Cloud
computing entrusts remote services with a user’s data, software
and computation.
End users access cloud-based applications through a web browser
or a light-weight desktop or mobile app while thebusiness
software and user’s data are stored on servers at a remote
location. Proponents claim that cloud computing allows companies
to avoid upfront infrastructure costs, and focus on projects that
differentiate their businesses instead of infrastructure.
Proponents also claim that cloud computing allows enterprises to
get the
manageability and less maintenance, and enables IT to more
rapidly adjust resources to meet fluctuating and unpredictable
business demand.
In the business model using software as a service (SaaS), users
are provided access to application software and databases. Cloud
providers manage the infrastructure and platforms that run the
applications. SaaS is sometimes referred to as “on-demand
software” and is usually priced on a pay-per-use basis. SaaS
providers generally price applications using a subscription fee.
Proponents claim SaaS allows a business the potential to reduce
IT operational costs by outsourcing hardware and software
maintenance and support to the cloud provider. This enables the
business to reallocate IT operations costs away from
hardware/software spending and personnel expenses, towards
meeting other goals. In addition, with applications hosted
centrally, updates can be released without the need for users to
install new software. One drawback of SaaS is that the users’
data are stored on the cloud provider’s server. As a result,
there could be unauthorized access to the data.
Cloud computing relies on sharing of resources to achieve
coherence and economies of scale similar to a utility (like
theelectricity grid) over a network.At the foundation of cloud
computing is the broader concept of converged infrastructure and
shared services.
History
The underlying concept of cloud computing dates back to the
1950s, when large-scale mainframe became available in academia
and corporations, accessible via thin clients / terminal
computers, often referred to as “dumb terminals”, because they
were used for communications but had no internal computational
capacities. To make more efficient use of costly mainframes, a
practice evolved that allowed multiple users to share both the
physical access to the computer from multiple terminals as well
as to share the CPU time. This eliminated periods of inactivity
on the mainframe and allowed for a greater return on the
investment. The practice of sharing CPU time on a mainframe
became known in the industry as time-sharing.
In the 1990s, telecommunications companies, who previously
offered primarily dedicated point-to-point data circuits, began
offering virtual private network (VPN) services with comparable
quality of service, but at a lower cost. By switching traffic as
they saw fit to balance server use, they could use overall
network bandwidth more effectively. They began to use the cloud
symbol to denote the demarcation point between what the provider
was responsible for and what users were responsible for. Cloud
computing extends this boundary to cover servers as well as the
network infrastructure.
As computers became more prevalent, scientists and technologists
explored ways to make large-scale computing power available to
more users through time sharing, experimenting with algorithms to
provide the optimal use of the infrastructure, platform and
applications with prioritized access to the CPU and efficiency
for the end users.
John McCarthy opined in the 1960s that “computation may someday
be organized as a public utility.” Almost all the modern-day
characteristics of cloud computing (elastic provision, provided
as a utility, online, illusion of infinite supply), the
comparison to the electricity industry and the use of public,
private, government, and community forms, were thoroughly
explored inDouglas Parkhill‘s 1966 book, The Challenge of the
Computer Utility. Other scholars have shown that cloud
computing’s roots go all the way back to the 1950s when scientist
Herb Grosch (the author of Grosch’s law) postulated that the
entire world would operate on dumb terminals powered by about 15
large data centers. Due to the expense of these powerful
computers, many corporations and other entities could avail
themselves of computing capability through time sharing and
several organizations, such as GE’s GEISCO, IBM subsidiary The
Service Bureau Corporation (SBC, founded in 1957), Tymshare
(founded in 1966), National CSS (founded in 1967 and bought by
Dun & Bradstreet in 1979), Dial Data (bought by Tymshare in
1968), and Bolt, Beranek and Newman (BBN) marketed time sharing
as a commercial venture.
The development of the Internet from being document centric via
semantic data towards more and more services was described as
“Dynamic Web”.This contribution focused in particular in the need
for better meta-data able to describe not only implementation
details but also conceptual details of model-based applications.
The ubiquitous availability of high-capacity networks, low-cost
computers and storage devices as well as the widespread adoption
of hardware virtualization, service-oriented
architecture,autonomic, and utility computing have led to a
tremendous growth in cloud computing.
After the dot-com bubble, Amazon played a key role in the
development of cloud computing by modernizing their data centers,
which, like most computer networks, were using as little as 10%
of their capacity at any one time, just to leave room for
occasional spikes. Having found that the new cloud architecture
resulted in significant internal efficiency improvements whereby
small, fast-moving “two-pizza teams” (teams small enough to feed
with two pizzas) could add new features faster and more easily,
Amazon initiated a new product development effort to provide
cloud computing to external customers, and launched Amazon Web
Service (AWS) on a utility computing basis in 2006.
In early 2008, Eucalyptus became the first open-source, AWS API-
compatible platform for deploying private clouds. In early 2008,
OpenNebula, enhanced in the RESERVOIR European Commission-funded
project, became the first open-source software for deploying
private and hybrid clouds, and for the federation of clouds. In
the same year, efforts were focused on providingquality of
service guarantees (as required by real-time interactive
applications) to cloud-based infrastructures, in the framework of
the IRMOS European Commission-funded project, resulting to
areal-time cloud environment. By mid-2008, Gartner saw an
opportunity for cloud computing “to shape the relationship among
consumers of IT services, those who use IT services and those who
sell them” and observed that “organizations are switching from
company-owned hardware and software assets to per-use service-
based models” so that the “projected shift to computing … will
result in dramatic growth in IT products in some areas and
significant reductions in other areas.”
On March 1, 2011, IBM announced the IBM SmartCloud framework to
support Smarter Planet.Among the various components of the
Smarter Computing foundation, cloud computing is a critical
piece.
Cloud Computing is the result of evolution and adoption of
existing technologies and paradigms. The goal of cloud computing
is to allow users to take beneļ¬t from all of these technologies,
without the need for deep knowledge about or expertise with each
one of them. The cloud aims to cut costs, and help the users
focus on their core business instead of being impeded by IT
obstacles.
The main enabling technologies for cloud computing are
virtualization and autonomic computing. Virtualization abstracts
the physical infrastructure, which is the most rigid component,
and makes it available as a soft component that is easy to use
and manage. By doing so, virtualization provides the agility
required to speed up IT operations, and reduces cost by
increasing infrastructureutilization. On the other hand,
autonomic computing automates the process through which the user
can provision resources on-demand. By minimizing user
involvement, automation speeds up the process and reduces the
possibility of human errors.
Users face difficult business problems every day. Cloud computing
adopts concepts from Service-oriented Architecture (SOA) that can
help the user break these problems into services that can be
integrated to provide a solution. Cloud computing provides all of
its resources as services, and makes use of the well-established
standards and best practices gained in the domain of SOA to allow
global and easy access to cloud services in a standardized way.
Cloud computing also leverages concepts from utility computing in
order to provide metrics for the services used. Such metrics are
at the core of the public cloud pay-per-use models. In addition,
measured services are an essential part of the feedback loop in
autonomic computing, allowing services to scale on-demand and to
perform automatic failure recovery.
Cloud computing is a kind of grid computing; it has evolved from
grid computing by addressing the QoS (quality of service) and
reliability problems. Cloud computing provides the tools and
technologies to build data/compute intensive parallel
applications with much more affordable prices compared to
traditional parallel computing techniques.
