Cloud computing is the delivery of computing as a service rather than a product,
whereby shared resources, software, and information are provided to computers
and other devices as a utility (like the electricity grid) over a network
(typically the Internet). Cloud
computing provides computation, software, data access, and storage services
that do not require end-user knowledge of the physical location and
configuration of the system that delivers the services. Parallels to this
concept can be drawn with the electricity grid, wherein end-users consume power
without needing to understand the component devices or infrastructure required
to provide the service.
Cloud
computing describes a new supplement, consumption, and delivery model for IT
services based on Internet protocols, and it typically involves provisioning of
dynamically scalable and often virtualized resources. It is a byproduct and
consequence of the ease-of-access to remote computing sites provided by the
Internet. This may take the form of web-based tools or applications that users
can access and use through a web browser as if the programs were installed locally
on their own computers.
Cloud computing providers deliver applications
via the internet, which are accessed from a web browser, while the business
software and data are stored on servers at a remote location. In some cases,
legacy applications (line of business applications that until now have been prevalent
in thin client Windows computing) are delivered via a screen-sharing
technology, while the computing resources are consolidated at a remote data
center location;
History
The
term "cloud" is used as a metaphor for the Internet, based on the
cloud drawing used in the past to represent the telephone network, and later to
depict the Internet in computer network diagrams as an abstraction of the
underlying infrastructure it represents. Cloud computing is a natural evolution
of the widespread adoption of virtualization, service-oriented architecture,
autonomic, and utility computing. Details are abstracted from end-users, who no
longer have need for expertise in, or control over, the technology
infrastructure "in the cloud" that supports them.
The
underlying concept of cloud computing dates back to the 1960s, when John McCarthy opined 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 in Douglas Parkhill's 1966 book, The
Challenge of the Computer Utility.
Cloud
computing types
Public
cloud
Public
cloud describes cloud computing in the traditional mainstream sense, whereby
resources are dynamically provisioned to the general public on a fine-grained,
self-service basis over the Internet, via web applications/web services, from an
off-site third-party provider who bills on a fine-grained utility computing
basis.
Community
cloud
Community
cloud shares infrastructure between several organizations from a specific
community with common concerns (security, compliance, jurisdiction) whether
managed internally or by a third-party and hosted internally or externally. The
costs are spread over fewer users than a public cloud (but more than a private
cloud), so only some of the benefits of cloud computing are realized.
Hybrid
cloud
Hybrid
cloud is a composition of two or more clouds (private, community, or public)
that remain unique entities but are bound together, offering the benefits of
multiple deployment models.
Private
cloud
Private
cloud is infrastructure operated solely for a single organization, whether
managed internally or by a third-party and hosted internally or externally.They
have attracted criticism because users "still have to buy, build, and
manage them" and thus do not benefit from lower up-front capital costs and
less hands-on management, essentially "[lacking] the economic model that
makes cloud computing such an intriguing concept".
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