9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 1/13

Cloud computing

Cloud computing metaphor: For a user, the network elementsrepresenting the provider­rendered services are invisible, as if obscuredby a cloud.

From Wikipedia, the free encyclopedia

Cloud computing is a model forenabling ubiquitous network access toa shared pool of configurablecomputing resources.[1] Cloudcomputing and storage solutionsprovide users and enterprises withvarious capabilities to store andprocess their data in third­party datacenters.[2] It relies on sharing ofresources to achieve coherenceand economies of scale, similar to autility (like the electricity grid) over anetwork.[3] At the foundation of cloudcomputing is the broader conceptof converged infrastructure and sharedservices.

Cloud computing, or in simplershorthand just "the cloud", alsofocuses on maximizing theeffectiveness of the shared resources.Cloud resources are usually not onlyshared by multiple users but are also dynamically reallocated per demand. This can work for allocatingresources to users. For example, a cloud computer facility that serves European users during Europeanbusiness hours with a specific application (e.g., email) may reallocate the same resources to serve NorthAmerican 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 byusing less power, air conditioning, rack space, etc. to maintain the system. With cloud computing, multipleusers can access a single server to retrieve and update their data without purchasing licenses for differentapplications.

The term "moving to cloud" also refers to an organization moving away from a traditional CAPEXmodel(buy the dedicated hardware and depreciate it over a period of time) to the OPEX model (use a sharedcloud infrastructure and pay as one uses it).[dubious – discuss]

Proponents claim that cloud computing allows companies to avoid upfront infrastructure costs, and focuson projects that differentiate their businesses instead of on infrastructure.[4] Proponents also claim thatcloud computing allows enterprises to get their applications up and running faster, with improvedmanageability and less maintenance, and enables IT to more rapidly adjust resources to meet fluctuating

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 2/13

and unpredictable business demand.[4][5][6] Cloud providers typically use a "pay as you go" model. This canlead to unexpectedly high charges if administrators do not adapt to the cloud pricing model.[7]

The present availability of high­capacity networks, low­cost computers and storage devices as well as thewidespread adoption of hardware virtualization,service­oriented architecture, and autonomic and utilitycomputing have led to a growth in cloud computing.[8][9][10] Companies can scale up as computing needsincrease and then scale down again as demands decrease.

Cloud vendors are experiencing growth rates of 50% per annum.[11]

Contents [hide]

1 History of cloud computing1.1 Origin of the term1.2 The 1970s1.3 The 1990s1.4 The New Millenium: 2000s

2 Similar concepts3 Characteristics4 Service models

4.1 Infrastructure as a service (IaaS)4.2 Platform as a service (PaaS)4.3 Software as a service (SaaS)

5 Cloud clients5.1 Cloud Provider Interface

6 Deployment models6.1 Private cloud6.2 Public cloud6.3 Hybrid cloud6.4 Others

6.4.1 Community cloud6.4.2 Distributed cloud6.4.3 Intercloud6.4.4 Multicloud

7 Architecture7.1 Cloud engineering

8 Security and privacy9 The future10 See also11 References12 External links

History of cloud computing [ edit source | edit ]

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 3/13

Origin of the term [ edit source | edit ]

The origin of the term cloud computing is unclear. The expression cloud is commonly used in science todescribe a large agglomeration of objects that visually appear from a distance as a cloud and describesany set of things whose details are not inspected further in a given context.[12] Another explanation is thatthe old programs draw network schematics surrounded the icons for servers with a circle, and a cluster ofservers in a network diagram had several overlapping circles, which resembled a cloud.[13]

In analogy to above usage the word cloud was used as a metaphor for the Internet and a standardizedcloud­like shape was used to denote a network on telephony schematics and later to depict the Internetin computer network diagrams. With this simplification, the implication is that the specifics of how the endpoints of a network are connected are not relevant for the purposes of understanding the diagram. Thecloud symbol was used to represent networks of computing equipment in the original ARPANET by as earlyas 1977,[14] and the CSNET by 1981[15]—both predecessors to the Internet itself.

References to cloud computing in its modern sense appeared as early as 1996, with the earliest knownmention in a Compaq internal document.[16]

The popularization of the term can be traced to 2006 when Amazon.com introduced the Elastic ComputeCloud.[17]

The 1970s [ edit source | edit ]

During the mid­1970s, time­sharing was popularly known as RJE (Remote Job Entry);[citation needed] thisterminology was mostly associated with large vendors such as IBM and DEC.[citation needed] IBM developedtheVM Operating System (first released in 1972) to provide time­sharing services[citation needed] via virtualmachines.

The 1990s [ edit source | edit ]

In the 1990s, telecommunications companies, who previously offered primarily dedicated point­to­pointdata circuits, began offering virtual private network(VPN) services with comparable quality of service, but ata lower cost. By switching traffic as they saw fit to balance server use, they could use overall networkbandwidth more effectively.[citation needed] They began to use the cloud symbol to denote the demarcationpoint between what the provider was responsible for and what users were responsible for. Cloudcomputing extends this boundary to cover all servers as well as the network infrastructure.[18]

As computers became more prevalent, scientists and technologists explored ways to make large­scalecomputing power available to more users through time­sharing.[citation needed] They experimented withalgorithms to optimize the infrastructure, platform, and applications to prioritize CPUs and increaseefficiency for end users.[19]

The New Millenium: 2000s [ edit source | edit ]

Since 2000 cloud computing has come into existence. In early 2008, NASA's OpenNebula, enhanced in theRESERVOIR European Commission­funded project, became the first open­source software for deploying

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 4/13

private and hybrid clouds, and for the federation of clouds.[20] In the same year, efforts were focused onproviding quality of service guarantees (as required by real­time interactive applications) to cloud­basedinfrastructures, in the framework of the IRMOS European Commission­funded project, resulting in a real­time cloud environment.[21] By mid­2008, Gartner saw an opportunity for cloud computing "to shape therelationship among consumers of IT services, those who use IT services and those who sell them"[22] andobserved that "organizations are switching from company­owned hardware and software assets to per­useservice­based models" so that the "projected shift to computing ... will result in dramatic growth in ITproducts in some areas and significant reductions in other areas."[23]

Microsoft Azure became available in late 2008.

In July 2010, Rackspace Hosting and NASA jointly launched an open­source cloud­software initiativeknown as OpenStack. The OpenStack project intended to help organizations offer cloud­computingservices running on standard hardware. The early code came from NASA's Nebula platform as well asfrom Rackspace's Cloud Files platform.[24]

On March 1, 2011, IBM announced the IBM SmartCloud framework to support Smarter Planet.[25]Amongthe various components of the Smarter Computing foundation, cloud computing is a critical piece.

On June 7, 2012, Oracle announced the Oracle Cloud.[26] While aspects of the Oracle Cloud are still indevelopment, this cloud offering is poised to be the first to provide users with access to an integrated set ofIT solutions, including the Applications (SaaS), Platform (PaaS), and Infrastructure (IaaS) layers.[27][28][29]

Similar concepts [ edit source | edit ]

Cloud computing is the result of the evolution and adoption of existing technologies and paradigms. Thegoal of cloud computing is to allow users to take benefit from all of these technologies, without the need fordeep knowledge about or expertise with each one of them. The cloud aims to cut costs, and helps theusers focus on their core business instead of being impeded by IT obstacles.[30]

The main enabling technology for cloud computing isvirtualization. Virtualization software separates aphysical computing device into one or more "virtual" devices, each of which can be easily used andmanaged to perform computing tasks. With operating system–level virtualization essentially creating ascalable system of multiple independent computing devices, idle computing resources can be allocatedand used more efficiently. Virtualization provides the agility required to speed up IT operations, andreduces cost by increasing infrastructure utilization. Autonomic computing automates the process throughwhich the user can provision resources on­demand. By minimizing user involvement, automation speedsup the process, reduces labor costs and reduces the possibility of human errors.[30]

Users routinely face difficult business problems. Cloud computing adopts concepts from Service­orientedArchitecture (SOA) that can help the user break these problems into services that can be integrated toprovide a solution. Cloud computing provides all of its resources as services, and makes use of the well­established standards and best practices gained in the domain of SOA to allow global and easy access tocloud services in a standardized way.

Cloud computing also leverages concepts from utility computing to provide metrics for the services used.

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 5/13

Such metrics are at the core of the public cloud pay­per­use models. In addition, measured services are anessential part of the feedback loop in autonomic computing, allowing services to scale on­demand and toperform automatic failure recovery.

Cloud computing is a kind of grid computing; it has evolved by addressing the QoS (quality of service)and reliability problems. Cloud computing provides the tools and technologies to build data/computeintensive parallel applications with much more affordable prices compared to traditional parallelcomputingtechniques.[30]

Cloud computing shares characteristics with:

Client–server model — Client–server computingrefers broadly to any distributed application thatdistinguishes between service providers (servers) and service requestors (clients).[31]

Grid computing — "A form of distributed and parallel computing, whereby a 'super and virtual computer'is composed of a cluster of networked,loosely coupled computers acting in concert to perform verylarge tasks."

Mainframe computer — Powerful computers used mainly by large organizations for critical applications,typically bulk data processing such as: census; industry and consumer statistics; police and secretintelligence services; enterprise resource planning; and financial transaction processing.Utility computing — The "packaging of computing resources, such as computation and storage, as ametered service similar to a traditional public utility, such as electricity."[32][33]

Peer­to­peer — A distributed architecture without the need for central coordination. Participants areboth suppliers and consumers of resources (in contrast to the traditional client–server model).

Characteristics [ edit source | edit ]

Cloud computing exhibits the following key characteristics:

Agility improves with users' ability to re­provision technological infrastructure resources.Cost reductions claimed by cloud providers. A public­cloud delivery model converts capital expenditureto operational expenditure.[34] This purportedly lowers barriers to entry, as infrastructure is typicallyprovided by a third party and does not need to be purchased for one­time or infrequent intensivecomputing tasks. Pricing on a utility computing basis is fine­grained, with usage­based options andfewer IT skills are required for implementation (in­house).[35] The e­FISCAL project's state­of­the­artrepository[36]contains several articles looking into cost aspects in more detail, most of them concludingthat costs savings depend on the type of activities supported and the type of infrastructure available in­house.Device and location independence[37] enable users to access systems using a web browserregardless of their location or what device they use (e.g., PC, mobile phone). As infrastructure is off­site(typically provided by a third­party) and accessed via the Internet, users can connect fromanywhere.[35]

Maintenance of cloud computing applications is easier, because they do not need to be installed oneach user's computer and can be accessed from different places.Multitenancy enables sharing of resources and costs across a large pool of users thus allowing for:

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 6/13

centralization of infrastructure in locations with lower costs (such as real estate, electricity, etc.)peak­load capacity increases (users need not engineer for highest possible load­levels)utilisation and efficiency improvements for systems that are often only 10–20% utilised.[38][39]

Performance is monitored, and consistent and loosely coupled architectures are constructedusing web services as the system interface.[35][40][41]

Productivity may be increased when multiple users can work on the same data simultaneously, ratherthan waiting for it to be saved and emailed. Time may be saved as information does not need to be re­entered when fields are matched, nor do users need to install application software upgrades to theircomputer.[42]

Reliability improves with the use of multiple redundant sites, which makes well­designed cloudcomputing suitable for business continuity anddisaster recovery.[43]

Scalability and elasticity via dynamic ("on­demand") provisioning of resources on a fine­grained, self­service basis in near real­time[44][45](Note, the VM startup time varies by VM type, location, OS andcloud providers[44]), without users having to engineer for peak loads.[46][47][48]

Security can improve due to centralization of data, increased security­focused resources, etc., butconcerns can persist about loss of control over certain sensitive data, and the lack of security for storedkernels. Security is often as good as or better than other traditional systems, in part because providersare able to devote resources to solving security issues that many customers cannot afford totackle.[49] However, the complexity of security is greatly increased when data is distributed over a widerarea or over a greater number of devices, as well as in multi­tenant systems shared by unrelatedusers. In addition, user access to security audit logs may be difficult or impossible. Private cloudinstallations are in part motivated by users' desire to retain control over the infrastructure and avoidlosing control of information security.

The National Institute of Standards and Technology's definition of cloud computing identifies "five essentialcharacteristics":

On­demand self­service. A consumer can unilaterally provision computing capabilities, such asserver time and network storage, as needed automatically without requiring human interactionwith each service provider.

Broad network access. Capabilities are available over the network and accessed throughstandard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g.,mobile phones, tablets, laptops, and workstations).

Resource pooling. The provider's computing resources are pooled to serve multipleconsumers using a multi­tenant model, with different physical and virtual resourcesdynamically assigned and reassigned according to consumer demand.

Rapid elasticity. Capabilities can be elastically provisioned and released, in some casesautomatically, to scale rapidly outward and inward commensurate with demand. To theconsumer, the capabilities available for provisioning often appear unlimited and can beappropriated in any quantity at any time.

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 7/13

Cloud­computing layers accessible within a stack

Measured service. Cloud systems automatically control and optimize resource use byleveraging a metering capability at some level of abstraction appropriate to the type of service(e.g., storage, processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported, providing transparency for both the provider andconsumer of the utilized service.

— National Institute of Standards and Technology[3]

Service models [ edit source | edit ]

Though service­oriented architecture advocates "everything as a service" (with theacronyms EaaS orXaaS or simply aas),[50] cloud­computing providers offer their "services" according todifferent models,[3][51][need quotation to verify] which happen to form a stack: infrastructure­, platform­ andsoftware­as­a­service.[52]

Infrastructure as a service (IaaS)[ edit source | edit ]See also: Category:Cloud infrastructure

In the most basic cloud­service model ­ and accordingto the IETF (Internet Engineering Task Force) ­providers of IaaS offer computers – physical or (moreoften) virtual machines – and other resources.(Ahypervisor, such as Xen, OracleVirtualBox, KVM,VMware ESX/ESXi, or Hyper­V runsthe virtual machines as guests. Pools of hypervisorswithin the cloud operational system can support largenumbers of virtual machines and the ability to scaleservices up and down according to customers' varyingrequirements. IaaS clouds often offer additionalresources such as a virtual­machine disk­imagelibrary,raw block storage, file or object storage, firewalls, load balancers, IP addresses, virtual local areanetworks (VLANs), and software bundles.[53]IaaS­cloud providers supply these resources on­demand fromtheir large pools of equipment installed in data centers. For wide­area connectivity, customers can useeither the Internet or carrier clouds (dedicatedvirtual private networks).

To deploy their applications, cloud users install operating­system images and their application software onthe cloud infrastructure. In this model, the cloud user patches and maintains the operating systems and theapplication software. Cloud providers typically bill IaaS services on a utility computing basis: cost reflectsthe amount of resources allocated and consumed.[54][55][56][57]

Platform as a service (PaaS) [ edit source | edit ]

Main article: Platform as a serviceSee also: Category:Cloud platforms

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 8/13

In the PaaS models, cloud providers deliver acomputing platform, typically including operating system,programming­language execution environment, database, and web server. Application developers candevelop and run their software solutions on a cloud platform without the cost and complexity of buying andmanaging the underlying hardware and software layers. With some PaaS offers like MicrosoftAzure and Google App Engine, the underlying computer and storage resources scale automatically tomatch application demand so that the cloud user does not have to allocate resources manually. Thelatter[which?] has also been proposed by an architecture aiming to facilitate real­time in cloudenvironments.[58][need quotation to verify] Even more specific application types can be provided via PaaS, suchas media encoding as provided by services like bitcodin.com[59] or media.io.[60]

Some integration and data management providers have also embraced specialized applications of PaaSas delivery models for data solutions. Examples include iPaaS and dPaaS. iPaaS (Integration Platform as aService) enables customers to develop, execute and govern integration flows.[61] Under the iPaaSintegration model, customers drive the development and deployment of integrations without installing ormanaging any hardware or middleware.[62] dPaaS (Data Platform as a Service) delivers integration—anddata­management—products as a fully managed service.[63] Under the dPaaS model, the PaaS provider,not the customer, manages the development and execution of data solutions by building tailored dataapplications for the customer. dPaaS users retain transparency and control over data through data­visualization tools.[64]

Software as a service (SaaS) [ edit source | edit ]

Main article: Software as a service

In the software as a service (SaaS) model, users gain access to application software and databases. Cloudproviders manage the infrastructure and platforms that run the applications. SaaS is sometimes referred toas "on­demand software" and is usually priced on a pay­per­use basis or using a subscriptionfee.[citation needed]

In the SaaS model, cloud providers install and operate application software in the cloud and cloud usersaccess the software from cloud clients. Cloud users do not manage the cloud infrastructure and platformwhere the application runs. This eliminates the need to install and run the application on the cloud user'sown computers, which simplifies maintenance and support. Cloud applications differ from otherapplications in their scalability—which can be achieved by cloning tasks onto multiple virtual machines atrun­time to meet changing work demand.[65] Load balancers distribute the work over the set of virtualmachines. This process is transparent to the cloud user, who sees only a single access­point. Toaccommodate a large number of cloud users, cloud applications can be multitenant, meaning that anymachine may serve more than one cloud­user organization.

The pricing model for SaaS applications is typically a monthly or yearly flat fee per user,[66] so pricesbecome scalable and adjustable if users are added or removed at any point.[67]

Proponents claim that SaaS gives a business the potential to reduce IT operational costs by outsourcinghardware and software maintenance and support to the cloud provider. This enables the business toreallocate IT operations costs away from hardware/software spending and from personnel expenses,towards meeting other goals. In addition, with applications hosted centrally, updates can be released

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3A… 9/13

Cloud computing types

without the need for users to install new software. One drawback of SaaS comes with storing the users'data on the cloud provider's server. As a result,[citation needed] there could be unauthorized access to thedata. For this reason, users are increasingly[quantify] adopting intelligent third­party key­management systems to help secure their data.[citation needed]

Cloud clients [ edit source | edit ]

See also: Category:Cloud clients

Users access cloud computing using networked client devices, such as desktopcomputers, laptops, tabletsand smartphones and any Ethernet enabled device such as Home AutomationGadgets. Some of these devices – cloud clients – rely on cloud computing for all or a majority of theirapplications so as to be essentially useless without it. Examples are thin clientsand the browser­based Chromebook. Many cloud applications do not require specific software on the client and instead usea web browser to interact with the cloud application. With Ajax and HTML5 theseWeb user interfaces canachieve a similar, or even better, look and feel to native applications. Some cloud applications, however,support specific client software dedicated to these applications (e.g., virtual desktop clients and most emailclients). Some legacy applications (line of business applications that until now have been prevalent in thinclient computing) are delivered via a screen­sharing technology.

Cloud Provider Interface [ edit source | edit ]

A Cloud Provider Interface (CPI) provide an abstraction from an underlying IaaS by defining a set offunctions for managing virtual machines life­cycle in which might run an elastic service.

References:

http://france.emc.com/collateral/white­paper/h12825­cloud­foundry­paas­vblock­wp.pdf ­ EMC whitepaper on Cloud Foundryhttps://bosh.io/ ­ BOSH, an open­source CPI for multiples PaaS

Deployment models [ edit source | edit ]

Private cloud is cloud infrastructureoperated solely for a singleorganization, whether managedinternally or by a third­party, andhosted either internally orexternally.[3] Undertaking a privatecloud project requires a significant leveland degree of engagement to virtualizethe business environment, and requiresthe organization to reevaluate decisionsabout existing resources. When done

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3… 10/13

right, it can improve business, but everystep in the project raises security issues that must be addressed to prevent serious vulnerabilities. Self­rundata centers[68] are generally capital intensive. They have a significant physical footprint, requiringallocations of space, hardware, and environmental controls. These assets have to be refreshedperiodically, resulting in additional capital expenditures. They have attracted criticism because users "stillhave to buy, build, and manage them" and thus do not benefit from less hands­onmanagement,[69] essentially "[lacking] the economic model that makes cloud computing such an intriguingconcept".[70][71]

Public cloud [ edit source | edit ]

A cloud is called a "public cloud" when the services are rendered over a network that is open for public use.Public cloud services may be free.[72] Technically there may be little or no difference between public andprivate cloud architecture, however, security consideration may be substantially different for services(applications, storage, and other resources) that are made available by a service provider for a publicaudience and when communication is effected over a non­trusted network. Generally, public cloud serviceproviders like Amazon AWS, Microsoft and Google own and operate the infrastructure at theirdatacenter and access is generally via the Internet. AWS and Microsoft also offer direct connect services called"AWS Direct Connect" and "Azure ExpressRoute" respectively, such connections require customers topurchase or lease a private connection to a peering point offered by the cloud provider.[35]

Hybrid cloud [ edit source | edit ]

Hybrid cloud is a composition of two or more clouds (private, community or public) that remain distinctentities but are bound together, offering the benefits of multiple deployment models. Hybrid cloud can alsomean the ability to connect collocation, managed and/or dedicated services with cloud resources.[3]

Gartner, Inc. defines a hybrid cloud service as a cloud computing service that is composed of somecombination of private, public and community cloud services, from different service providers.[73] A hybridcloud service crosses isolation and provider boundaries so that it can't be simply put in one category ofprivate, public, or community cloud service. It allows one to extend either the capacity or the capability of acloud service, by aggregation, integration or customization with another cloud service.

Varied use cases for hybrid cloud composition exist. For example, an organization may store sensitiveclient data in house on a private cloud application, but interconnect that application to a businessintelligence application provided on a public cloud as a software service.[74] This example of hybrid cloudextends the capabilities of the enterprise to deliver a specific business service through the addition ofexternally available public cloud services. Hybrid cloud adoption depends on a number of factors such asdata security and compliance requirements, level of control needed over data, and the applications anorganization uses.[75]

Another example of hybrid cloud is one where IT organizations use public cloud computing resources tomeet temporary capacity needs that can not be met by the private cloud.[76] This capability enables hybridclouds to employ cloud bursting for scaling across clouds.[3] Cloud bursting is an application deploymentmodel in which an application runs in a private cloud or data center and "bursts" to a public cloud when the

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3… 11/13

demand for computing capacity increases. A primary advantage of cloud bursting and a hybrid cloud modelis that an organization only pays for extra compute resources when they are needed.[77] Cloud burstingenables data centers to create an in­house IT infrastructure that supports average workloads, and usecloud resources from public or private clouds, during spikes in processing demands.[78]

The specialized model of hybrid cloud, which is built atop heterogeneous hardware, is called "Cross­platform Hybrid Cloud". A cross­platform hybrid cloud is usually powered by different CPU architectures, forexample, x86­64 and ARM, underneath. Users can transparently deploy applications without knowledge ofthe cloud's hardware diversity.[79] This kind of cloud emerges from the raise of ARM­based system­on­chipfor server­class computing.

Others [ edit source | edit ]

Community cloud [ edit source | edit ]

Community cloud shares infrastructure between several organizations from a specific community withcommon concerns (security, compliance, jurisdiction, etc.), whether managed internally or by a third­party,and either hosted internally or externally. The costs are spread over fewer users than a public cloud (butmore than a private cloud), so only some of the cost savings potential of cloud computing are realized.[3]

Distributed cloud [ edit source | edit ]

A cloud computing platform can be assembled from a distributed set of machines in different locations,connected to a single network or hub service. It is possible to distinguish between two types of distributedclouds: public­resource computing and volunteer cloud.

Public­resource computing: This type of distributed cloud results from an expansive definition ofcloud computing, because they are more akin to distributed computing than cloud computing.Nonetheless, it is considered a sub­class of cloud computing, and some examples include distributedcomputing platforms such asBOINC and Folding@Home.Volunteer cloud: Volunteer cloud computing is characterized as the intersection of public­resourcecomputing and cloud computing, where a cloud computing infrastructure is built using volunteeredresources. Many challenges arise from this type of infrastructure, because of the volatility of theresources used to built it and the dynamic environment it operates in. It can also be called peer­to­peerclouds, or ad­hoc clouds. An interesting effort in such direction is Cloud@Home, it aims to implement acloud computing infrastructure using volunteered resources providing a business­model to incentivizecontributions through financial restitution [80]

Intercloud [ edit source | edit ]

Main article: Intercloud

The Intercloud[81] is an interconnected global "cloud of clouds"[82][83] and an extension of the Internet"network of networks" on which it is based. The focus is on direct interoperability between public cloudservice providers, more so than between providers and consumers (as is the case for hybrid­ and multi­cloud).[84][85][86]

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3… 12/13

Cloud computing sample architecture

Multicloud [ edit source | edit ]

Main article: Multicloud

Multicloud is the use of multiple cloud computing services in a single heterogeneous architecture to reducereliance on single vendors, increase flexibility through choice, mitigate against disasters, etc. It differs fromhybrid cloud in that it refers to multiple cloud services, rather than multiple deployment modes (public,private, legacy).[87][88]

Architecture [ edit source | edit ]

Cloud architecture,[89] the systemsarchitecture of the software systems involved inthe delivery of cloud computing, typically involvesmultiple cloud components communicating witheach other over a loose coupling mechanism suchas a messaging queue. Elastic provision impliesintelligence in the use of tight or loose coupling asapplied to mechanisms such as these and others.

Cloud engineering [ edit source | edit ]

Cloud engineering is the applicationof engineeringdisciplines to cloud computing. Itbrings a systematic approach to the high­levelconcerns of commercialization, standardization, and governance in conceiving, developing, operating andmaintaining cloud computing systems. It is a multidisciplinary method encompassing contributions fromdiverse areas such as systems, software, web, performance,information, security, platform, risk,and qualityengineering.

Security and privacy [ edit source | edit ]

Main article: Cloud computing issues

Cloud computing poses privacy concerns because the service provider can access the data that is on thecloud at any time. It could accidentally or deliberately alter or even delete information.[90] Many cloudproviders can share information with third parties if necessary for purposes of law and order even without awarrant. That is permitted in their privacy policies which users have to agree to before they start usingcloud services.[91] Solutions to privacy include policy and legislation as well as end users' choices for howdata is stored.[90] Users can encrypt data that is processed or stored within the cloud to preventunauthorized access. [2][90]

According to the Cloud Security Alliance, the top three threats in the cloud are "Insecure Interfaces andAPI's", "Data Loss & Leakage", and "Hardware Failure" which accounted for 29%, 25% and 10% of allcloud security outages respectively — together these form shared technology vulnerabilities. In a cloudprovider platform being shared by different users there may be a possibility that information belonging to

9/15/2015 Cloud computing ­ Wikipedia, the free encyclopedia

data:text/html;charset=utf­8,%3Ch1%20id%3D%22firstHeading%22%20class%3D%22firstHeading%22%20lang%3D%22en%22%20style%3D%22color%3… 13/13

different customers resides on same data server. Therefore, Information leakage may arise by mistakewhen information for one customer is given to other.[92] Additionally, Eugene Schultz, chief technologyofficer at Emagined Security, said that hackers are spending substantial time and effort looking for ways topenetrate the cloud. "There are some real Achilles' heels in the cloud infrastructure that are making bigholes for the bad guys to get into". Because data from hundreds or thousands of companies can be storedon large cloud servers, hackers can theoretically gain control of huge stores of information through a singleattack — a process he called "hyperjacking".

There is the problem of legal ownership of the data (If a user stores some data in the cloud, can the cloudprovider profit from it?). Many Terms of Service agreements are silent on the question of ownership.[93]

Physical control of the computer equipment (private cloud) is more secure than having the equipment offsite and under someone else's control (public cloud). This delivers great incentive to public cloudcomputing service providers to prioritize building and maintaining strong management of secureservices.[94] Some small businesses that don't have expertise in IT security could find that it's more securefor them to use a public cloud.

There is the risk that end users don't understand the issues involved when signing on to a cloud service(persons sometimes don't read the many pages of the terms of service agreement, and just click "Accept"without reading). This is important now that cloud computing is becoming popular and required for someservices to work, for example for an intelligent personal assistant (Apple's Siri or Google Now).

Fundamentally private cloud is seen as more secure with higher levels of control for the owner, howeverpublic cloud is seen to be more flexible and requires less time and money investment from the user.[95]

The future [ edit source | edit ]

According to Gartners Hype cycle, cloud computing has reached a maturity that leads it into a productivephase. This means that most of the main issues with cloud computing have been addressed to a degreethat clouds have become interesting for full commercial exploitation. This however does not mean that allthe problems listed above have actually been solved, only that the according risks can be tolerated to acertain degree.[96] Cloud computing is therefore still as much a research topic, as it is a marketoffering.[97] What is clear through the evolution of Cloud Computing services is that the CTO is a majordriving force behind Cloud adoption.[98] The major Cloud technology developers continue to invest billionsa year in Cloud R&D; for example, in 2011 Microsoft committed 90% of its $9.6bn R&D budget toCloud.[99] Additionally, more industries are turning to cloud technology as an efficient way to improvequality services due to its capabilities to reduce overhead costs, downtime, and automate infrastructuredeployment.[100]