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Cloud computing, also known as on-demand computing, is a kind of Internet-based computing, where shared resources,data and information are provided to computers and other devices on-demand. It is a model for enabling ubiquitous, on-demand access to a shared pool of configurable computing resources.〔http://csrc.nist.gov/publications/nistpubs/800-145/SP800-145.pdf〕 Cloud computing and storage solutions provide users and enterprises with various capabilities to store and process their data in third-party data centers.〔M. Haghighat, S. Zonouz, & M. Abdel-Mottaleb (2015). (CloudID: Trustworthy Cloud-based and Cross-Enterprise Biometric Identification ). Expert Systems with Applications, 42(21), 7905–7916.〕 It relies on sharing of resources to achieve coherence and economies of scale, similar to a utility (like the electricity grid) over a network.〔(【引用サイトリンク】url=http://csrc.nist.gov/publications/nistpubs/800-145/SP800-145.pdf )〕 At the foundation of cloud computing is the broader concept of converged infrastructure and shared services. Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications and services) that can be rapidly provisioned and released with minimal management effort. Cloud computing, or in simpler shorthand just "the cloud", also focuses on maximizing the effectiveness of the shared resources. Cloud resources are usually not only shared by multiple users but are also dynamically reallocated per demand. This can work for allocating resources to users. For example, a cloud computer facility that serves European users during European business hours with a specific application (e.g., email) may reallocate the same resources to serve North American users during North America's business hours with a different application (e.g., a web server). This approach helps maximize the use of computing power while reducing the overall cost of resources by using less power, air conditioning, rack space, etc. to maintain the system. With cloud computing, multiple users can access a single server to retrieve and update their data without purchasing licenses for different applications. The term "moving to cloud" also refers to an organization moving away from a traditional CAPEX model (buy the dedicated hardware and depreciate it over a period of time) to the OPEX model (use a shared cloud infrastructure and pay as one uses it). Proponents claim that cloud computing allows companies to avoid upfront infrastructure costs, and focus on projects that differentiate their businesses instead of on infrastructure. Proponents also claim that cloud computing allows enterprises to get their applications up and running faster, with improved manageability and less maintenance, and enables IT to more rapidly adjust resources to meet fluctuating and unpredictable business demand.〔 Cloud providers typically use a "pay as you go" model. This can lead to unexpectedly high charges if administrators do not adapt to the cloud pricing model.〔(【引用サイトリンク】title=Where's The Rub: Cloud Computing's Hidden Costs )〕 The present availability of high-capacity networks, low-cost computers and storage devices as well as the widespread adoption of hardware virtualization, service-oriented architecture, and autonomic and utility computing have led to a growth in cloud computing.〔(【引用サイトリンク】title= Gartner Says Cloud Computing Will Be As Influential As E-business )〕 Companies can scale up as computing needs increase and then scale down again as demands decrease. Cloud computing has now become a highly demanded service or utility due to the advantages of high computing power, cheap cost of services, high performance, scalability, accessibility as well as availability. Cloud vendors are experiencing growth rates of 50% per annum.〔(【引用サイトリンク】url=http://www.fsn.co.uk/channel_outsourcing/the_economy_is_flat_so_why_are_financials_cloud_vendors_growing_at_more_than_90_percent_per_annum#.UbmtsPlJPGA/ )〕 But due to being in a stage of infancy, it still has some pitfalls which need to be given proper attention to make cloud computing services more reliable and user friendly. ==History of cloud computing== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cloud computing」の詳細全文を読む スポンサード リンク
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