Cloud Computing

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 benefit 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.