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[日期:2009-01-19] 来源:Wikipedia  作者: [字体: ]

cloud computing is Internet ("cloud") based development and use of computer technology ("computing"). It is a style of computing in which resources are provided “as a service[1] over the Internet[2] to users who need not have knowledge of, expertise in, or control over the technology infrastructure ("in the cloud") that supports them[3].

It is a general concept that incorporates software as a service (SaaS), Web 2.0 and other recent, well-known technology trends, in which the common theme is reliance on the Internet for satisfying the computing needs of the users. An often-quoted example is Google Apps, which provides common business applications online that are accessed from a web browser, while the software and data are stored on Google servers.

The cloud is a metaphor for the Internet, based on how it is depicted in computer network diagrams, and is an abstraction for the complex infrastructure it conceals.[4].



[edit] Brief

[edit] Comparisons

Cloud computing is often confused with grid computing, ("a form of distributed computing whereby a 'super and virtual computer' is composed of a cluster of networked, loosely-coupled computers, acting in concert to perform very large tasks"), utility computing (the "packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility such as electricity")[5] and autonomic computing ("computer systems capable of self-management").[6]

Indeed many cloud computing deployments as of 2009[update] depend on grids, have autonomic characteristics and bill like utilities — but cloud computing can be seen as a natural next step from the grid-utility model.[7] Some successful cloud architectures have little or no centralised infrastructure or billing systems whatsoever, including peer-to-peer networks like BitTorrent and Skype and volunteer computing like SETI@home.[8]

[edit] Architecture

The majority of cloud computing infrastructure as of 2009[update] consists of reliable services delivered through data centers and built on servers with different levels of virtualization technologies. The services are accessible anywhere in the world, with The Cloud appearing as a single point of access for all the computing needs of consumers. Commercial offerings need to meet the quality of service requirements of customers and typically offer service level agreements.[9] Open standards and open source software are also critical to the growth of cloud computing.[10]

[edit] Characteristics

As customers generally do not own the infrastructure, they merely access or rent, they can avoid capital expenditure and consume resources as a service, paying instead for what they use. Many cloud-computing offerings have adopted the utility computing model, which is analogous to how traditional utilities like electricity are consumed, while others are billed on a subscription basis. Sharing "perishable and intangible" computing power among multiple tenants can improve utilization rates, as servers are not left idle, which can reduce costs significantly while increasing the speed of application development. A side effect of this approach is that "computer capacity rises dramatically" as customers do not have to engineer for peak loads.[11] Adoption has been enabled by "increased high-speed bandwidth" which makes it possible to receive the same response times from centralized infrastructure at other sites.

[edit] Companies

Providers including Amazon, Google and Microsoft exemplify the use of cloud computing.[12] It is being adopted by individual users through large enterprises including General Electric, L'Oréal, and Procter & Gamble.[13][14]

[edit] History

The Cloud[15] has served as a metaphor for the Internet,[16] deriving from its common depiction in network diagrams as a cloud outline.[4]

The underlying concept dates back to 1960 when John McCarthy opined that "computation may someday be organized as a public utility"; indeed it shares characteristics with service bureaus which date back to the 1960s. The term cloud had already come into commercial use in the early 1990s to refer to large ATM networks.[17] By the turn of the 21st century, the term "cloud computing" had started to appear,[18] although most of the focus at this time was on Software as a service.

Amazon.com played a key role in the development of cloud computing by modernizing their data centres after the dot-com bubble and, having found that the new cloud architecture resulted in significant internal efficiency improvements, providing access to their systems by way of Amazon Web Services in 2002 on a utility computing basis.[19]

2007 saw increased activity, with Google, IBM, and a number of universities embarking on a large scale cloud computing research project,[20] around the time the term started gaining popularity in the mainstream press. It was a hot topic by mid-2008 and numerous cloud computing events had been scheduled.[21]

In August 2008 Gartner observed that "organisations are switching from company-owned hardware and software assets to per-use service-based models" and that the "projected shift to cloud computing will result in dramatic growth in IT products in some areas and in significant reductions in other areas".[22]

[edit] Political issues

The Cloud spans many borders and "may be the ultimate form of globalization"[23]. As such it becomes subject to complex geopolitical issues: providers must satisfy a myriad of regulatory environments in order to deliver service to a global market. This dates back to the early days of the Internet, where libertarian thinkers felt that "cyberspace was a distinct place calling for laws and legal institutions of its own"; author Neal Stephenson envisaged this as a tiny island data haven called Kinakuta in his science-fiction classic novel Cryptonomicon[23].

Despite efforts (such as US-EU Safe Harbor) to harmonise the legal environment, providers like Amazon Web Services cater as of 2009[update] to the major markets (typically the United States and the European Union) by deploying local infrastructure and allowing customers to select "availability zones"[24]. Nonetheless there are still concerns about security and privacy from individual through governmental level, e.g., the USA PATRIOT Act and use of national security letters and the Electronic Communications Privacy Act's Stored Communications Act.

[edit] Legal issues

In March 2007, Dell applied to trademark the term '"cloud computing" (U.S. Trademark 77,139,082) in the United States. The "Notice of Allowance" it received in July 2008 got canceled on August 6, resulting in a formal rejection of the trademark application less than a week later.

Richard Stallman, founder of the Free Software Foundation, believes that cloud computing endangers liberties because users sacrifice their privacy and personal data to a third party. [25]. In November 2007, the Free Software Foundation released the Affero General Public License, a version of GPLv3 designed to close a perceived legal loophole associated with Free software designed to be run over a network, particularly software as a service. An application service provider is required to release any changes they make to Affero GPL open source code.

[edit] Risk mitigation

Corporations or end-users wishing to avoid losing or not being able to access their data should research vendor's policies on data security before using vendor services. The technology analyst and consulting firm, Gartner, lists seven security issues which one should discuss with a cloud-computing vendor:

  1. Privileged user access—inquire about who has specialized access to data and about the hiring and management of such administrators
  2. Regulatory compliance—make sure a vendor is willing to undergo external audits and/or security certifications
  3. Data location—ask if a provider allows for any control over the location of data
  4. Data segregation—make sure that encryption is available at all stages and that these “encryption schemes were designed and tested by experienced professionals.”
  5. Recovery—find out what will happen to data in the case of a disaster; do they offer complete restoration and, if so, how long that would take
  6. Investigative Support—inquire as to whether a vendor has the ability to investigate any inappropriate or illegal activity
  7. Long-term viability—ask what will happen to data if the company goes out of business; how will data be returned and in what format[26]

In practice, one can best determine data-recovery capabilities by experiment: asking to get back old data, seeing how long it takes, and verifying that the checksums match the original data. Determining data security is harder. A tactic not covered by Gartner is: encrypt the data yourself. If you encrypt the data using a trusted algorithm, then regardless of the service provider's security and encryption policties, the data will only be accessible with the decryption keys. This leads to a follow-on problem: managing private keys in a pay-on-demand computing infrastructure.

[edit] Key characteristics

  • Customers minimize capital expenditure; this lowers barriers to entry, as infrastructure is owned by the provider and does not need to be purchased for one-time or infrequent intensive computing tasks. Services are typically available to or specifically targeted to retail consumers and small businesses.
  • Device and location independence[27] enable users to access systems regardless of their location or what device they are using, e.g., PC, mobile.
  • Multi-tenancy enables sharing of resources and costs among a large pool of users, allowing for:
    • Centralization of infrastructure in areas with lower costs (such as real estate, electricity, etc.)
    • Peak-load capacity increases (users need not engineer for highest possible load-levels)
    • Utilisation and efficiency improvements for systems that are often only 10-20% utilised.[19]
  • On-demand allocation and de-allocation of CPU, storage and network bandwidth
  • Performance is monitored and consistent, but can suffer from insufficient bandwidth or high network load.
  • Reliability improves through the use of multiple redundant sites, which makes it suitable for business continuity and disaster recovery,[28]. Nonetheless, most major cloud computing services have suffered outages and IT and business managers are able to do little when they are affected.[29].[30]
  • Scalability meets changing user demands quickly without users having to engineer for peak loads.
  • Security typically improves due to centralization of data[31], increased security-focused resources, etc., but raises concerns about loss of control over certain sensitive data. Providers typically log accesses, but accessing the audit logs themselves can be difficult or impossible.
  • Sustainability comes about through improved resource utilisation, more efficient systems, and carbon neutrality[32][33]. Nonetheless, computers and associated infrastructure are major consumers of energy[34].

[edit] Components

[edit] Application

"See also" category: Cloud applications

A cloud application leverages The Cloud in software architecture, often eliminating the need to install and run the application on the customer's own computer, thus alleviating the burden of software maintenance, ongoing operation, and support. For example:

[edit] Client

"See also" category: Cloud clients

A cloud client consists of computer hardware and/or computer software which relies on The Cloud for application delivery, or which is specifically designed for delivery of cloud services, and which in either case is essentially useless without it.[35] For example:

[edit] Infrastructure

"See also" category: Cloud infrastructure

Cloud infrastructure, such as Infrastructure as a service, is the delivery of computer infrastructure, typically a platform virtualization environment, as a service.[43] For example:

[edit] Platform

"See also" category: Cloud platforms

A cloud platform, such as Platform as a service, the delivery of a computing platform, and/or solution stack as a service, facilitates deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers.[44] For example:

[edit] Service

"See also" category: Cloud services

A cloud service, such as Web Service, is "software system[s] designed to support interoperable machine-to-machine interaction over a network"[45] which may be accessed by other cloud computing components, software, e.g., Software plus services, or end users directly.[46] For example:

[edit] Storage

"See also" category: Cloud storage

Cloud storage involves the delivery of data storage as a service, including database-like services, often billed on a utility computing basis, e.g., per gigabyte per month.[47] For example:

[edit] Architecture

Cloud architecture,[48] the systems architecture of the software systems involved in the delivery of cloud computing, comprises hardware and software designed by a cloud architect who typically works for a cloud integrator. It typically involves multiple cloud components communicating with each other over application programming interfaces, usually web services.[49]

This closely resembles the Unix philosophy of having multiple programs doing one thing well and working together over universal interfaces. Complexity is controlled and the resulting systems are more manageable than their monolithic counterparts.

Cloud architecture extends to the client, where web browsers and/or software applications access cloud applications.

Cloud storage architecture is loosely coupled, where metadata operations are centralized enabling the data nodes to scale into the hundreds, each independently delivering data to applications or users.

[edit] Roles

[edit] Provider

"See also" category: Cloud computing providers

A cloud computing provider or cloud computing service provider owns and operates live cloud computing systems to deliver service to third parties. Usually this requires significant resources and expertise in building and managing next-generation[weasel words] data centers. Some organisations realise a subset of the benefits of cloud computing by becoming "internal" cloud providers and servicing themselves, although they do not benefit from the same economies of scale and still have to engineer for peak loads. The barrier to entry is also significantly higher with capital expenditure required and billing and management creates some overhead. Nonetheless, significant operational efficiency and agility advantages can be realised, even by small organisations, and server consolidation and virtualization rollouts are already well underway.[50] Amazon.com was the first such provider, modernising its data centers which, like most computer networks, were using as little as 10% of its capacity at any one time just to leave room for occasional spikes. This allowed small, fast-moving groups to add new features faster and easier, and they went on to open it up to outsiders as Amazon Web Services in 2002 on a utility computing basis.[19]

The companies listed in the Components section are providers.

[edit] User

"See also" category: Cloud computing users

A user is a consumer of cloud computing.[35] The privacy of users in cloud computing has become of increasing concern.[51][52] The rights of users is also an issue, which is being addressed via a community effort to create a bill of rights, currently in draft.[53][54]

[edit] Vendor

"See also" category: Cloud computing vendors

A vendor sells products and services that facilitate the delivery, adoption and use of cloud computing.[55] For example:

[edit] Standards

"See also" category: Cloud standards

Cloud standards, a number of existing, typically lightweight, open standards, have facilitated the growth of cloud computing, including:[57]

[edit] References

  1. ^ Gartner Says Cloud Computing Will Be As Influential As E-business
  2. ^ What's the difference Between Cloud Computing and SaaS?
  3. ^ Distinguishing Cloud Computing from Utility Computing
  4. ^ a b The Internet Cloud
  5. ^ "It's probable that you’ve misunderstood 'Cloud Computing' until now". TechPluto.
  6. ^ What's In A Name? Utility vs. Cloud vs Grid
  7. ^ I.B.M. to Push ‘Cloud Computing,’ Using Data From Afar
  8. ^ ACM Ubiquity: Emergence of The Academic Computing Cloud
  9. ^ Rajkumar Buyya1, Chee Shin Yeo1, Srikumar Venugopal1. "Market-Oriented Cloud Computing: Vision, Hype, and Reality for Delivering IT Services as Computing Utilities" (PDF). 9 Department of Computer Science and Software Engineering, The University of Melbourne, Australia. Retrieved on 2008-07-31.
  10. ^ Open source fuels growth of cloud computing, software-as-a-service
  11. ^ Cloud Computing: The Evolution of Software-as-a-Service
  12. ^ [1]
  13. ^ Google Apps makes its way into big business
  14. ^ Google, Inc. Q2 2008 Earnings Call
  15. ^ Cloud Computing: When Computers Really Do Rule
  16. ^ What cloud computing really means
  17. ^ July, 1993 meeting report from the IP over ATM working group of the IETF
  18. ^ Internet Critic Takes on Microsoft
  19. ^ a b c Jeff Bezos' Risky Bet
  20. ^ Google and I.B.M. Join in ‘Cloud Computing’ Research
  21. ^ Keep an eye on cloud computing
  22. ^ Gartner Says Worldwide IT Spending On Pace to Surpass $3.4 Trillion in 2008
  23. ^ a b Computers without borders
  24. ^ Feature Guide: Amazon EC2 Availability Zones
  25. ^ Cloud computing is a trap, warns GNU founder Richard Stallman, Guardian, September 30, 2008
  26. ^ Brodkin, Jon. "Gartner: Seven cloud-computing security risks | InfoWorld | News | 2008-07-02 | ." InfoWorld - Business technology, IT news, product reviews and enterprise IT strategies. 3 Dec. 2008 <http://www.infoworld.com/article/08/07/02/Gartner_Seven_cloudcomputing_security_risks_1.html>.
  27. ^ The new geek chic: Data centers
  28. ^ Cloud Computing: Small Companies Take Flight
  29. ^ Google Apps Admins Jittery About Gmail, Hopeful About Future
  30. ^ New Resource, Born of a Cloud Feud
  31. ^ Exari: Death By Laptop
  32. ^ Google to go carbon neutral by 2008
  33. ^ What is Cloud Computing?
  34. ^ Shut off your computer
  35. ^ a b Nimbus Cloud Guide
  36. ^ Google's Open Source Android OS Will Free the Wireless Web
  37. ^ In Sync to Pierce the Cloud
  38. ^ Microsoft demos mobile cloud sync client
  39. ^ CherryPal brings cloud computing to the masses
  40. ^ Zonbu has alluring features, price
  41. ^ GOS cloud computing
  42. ^ Google Chrome Aims to Break Microsoft Windows
  43. ^ EMC buys Pi and forms a cloud computing group
  44. ^ Google angles for business users with 'platform as a service'
  45. ^ "Web Services Glossary".
  46. ^ The Emerging Cloud Service Architecture
  47. ^ Google, Microsoft and Apple building online storage havens: you win
  48. ^ Building GrepTheWeb in the Cloud, Part 1: Cloud Architectures
  49. ^ Cloud Maturity Is Accelerating: More Than Just Reaction To The Hype?
  50. ^ ACM Queue - Beyond Server Consolidation
  51. ^ ORGs for Scalable, Robust, Privacy-Friendly Client Cloud Computing
  52. ^ Google Privacy Practices Worse Than ISP Snooping, AT&T Charges
  53. ^ Draft Cloud Computing: Bill of Rights Now Available
  54. ^ Johnston, Sam; Urquhart, James; Wellner, Rich (2008-09-16). "Cloud Computing:Bill of rights". Retrieved on 2008-09-16.
  55. ^ List of Cloud Platforms, Providers and Enablers
  56. ^ Red Hat chief: 'The clouds will all run Linux'
  57. ^ The Cloud and Standards
  58. ^ Lock-in, security loom as dark side of Compute Cloud
  59. ^ LinuxWorld/Next Generation Data Center attendees get schooled in cloud computing

[edit] External links

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