http://en.wikipedia.org/wiki/Cloud_computing
Cloud computing is location independent
computing, whereby shared servers provide resources, software, and data to
computers and other devices on demand, as with the
electricity grid. Or more simply, remote computing. Cloud computing is a natural evolution of the widespread adoption of
virtualization,
service-oriented architecture and
utility computing. Details are abstracted from consumers, who no longer have need for expertise in, or control over, the technology infrastructure "in the cloud" that supports them.<sup id="cite_ref-0" class="reference">[1]</sup>
Cloud computing describes a new supplement, consumption, and delivery model for
IT services based on the Internet, and it typically involves over-the-Internet provision of dynamically
scalable and often virtualized resources.<sup id="cite_ref-gartner_1-0" class="reference">[2]</sup><sup
id="cite_ref-really_2-0" class="reference">[3]</sup> It is a byproduct and consequence of the ease-of-access to remote
computing sites provided by the Internet.<sup id="cite_ref-3" class="reference">[4]</sup>
This frequently takes the form of web-based tools or applications that users can access and use through a
web browser as if it were a program installed locally on their own computer.<sup id="cite_ref-simple_4-0" class="reference">[5]</sup>
The National Institute of Standards and Technology (NIST) provides a somewhat more objective and specific definition here.<sup id="cite_ref-5" class="reference">[6]</sup>
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,<sup id="cite_ref-6" class="reference">[7]</sup>
and later to depict the Internet in
computer network diagrams as an
abstraction of the underlying infrastructure it represents.<sup id="cite_ref-7" class="reference">[8]</sup>
Typical cloud computing providers deliver common
business applications online that are accessed from another Web service or software like a
Web browser, while the
software and
data are stored on
servers.
Most cloud computing infrastructures consist of services delivered through common centers and built on servers. Clouds often appear as single points of access for consumers' computing needs. Commercial offerings are generally expected to meet
quality of service (QoS) requirements of customers, and typically include
service level agreements (SLAs).<sup id="cite_ref-ccpaper_8-0" class="reference">[9]</sup>
Frank Xu Lei--谦卑若愚，好学若饥
专注于.NET平台下分布式应用系统开发和企业应用系统集成
Focus on Distributed Applications Development and EAI based on .NET
【老徐的网站】：http://www.frankxulei.com/
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