Cloud ComputingChen PengSchool of Information Science and Technology, YanChenNormal College,YanChen ChinaEmail:Abstract--Cloud computing is a new computing model；it is developed based on grid computing．We introduced the development history of cloud computing and its application situation and gave a new definition；took google’s cloud computing techniques as an example，summed up key techniques，such as data storage technology(Google )，data management technology(BigTable)，as well as programming model and task scheduling model(Map—Reduce)，used in cloud computing；and analyzed the differences among cloud computing,grid computing and traditional super-computing，and fingered out the further development prospects of cloud computing．Key words:cloud computing；data storage；data management；programming modelⅠ. DefinitionCloud computing is the development of distributed computing, parallel processing, and grid computing, which represents an emerging business computing modelⅡ. Cloud Computing SummaryCloud computing is a kind of network service and is a trend for future computing Scalability matters in cloud computing technology Users focus on application development Services are not known geographicallyⅢ. The specific characteristics1)Data in the cloud: not afraid to lose, do not have to back up,you can restore at any point;2)Software in the cloud: You do not have to download and updateyourself ；3)Ubiquitous computing: at any time, any place, any device, login to enjoy computing services;4)Powerful computing: unlimited space, unlimited speedⅣ. The main forms of service1)Software as a Service(SaaS)2)SaaS service providers deploy application software on theserver, users on demand ordered from the manufacturer via the Internet, service providers charge based on customer's needs, and to provide customers with the software through a browser.3)Platform as a Service(PaaS)4)Manufacturers provide a development environment, serverplatforms, hardware resources services to customers, custom develop their own application and pass through its servers and the Internet to other customers5)Infrastructure services(IaaS)6)"Cloud" infrastructure consisting of multiple servers, providemeasurement services to customers.Ⅴ. Characteristics1)In general, cloud computing customers do not own the physicalinfrastructure, instead avoiding capital expenditure by renting usage from a third-party provider. They consume resources as a service and pay only for resources that they use. Many cloud-computing offerings employ the utility computing model, which is analogous to how traditional utility services (such as electricity) are consumed, whereas others bill on a subscription basis. Sharing "perishable and intangible" computing power among multiple tenants can improve utilization rates, as servers are not unnecessarily left idle (which can reduce costs significantly while increasing the speed of application development). A side-effect of this approach is that overall computer usage rises dramatically, as customers do not have to engineer for peak load limits. In addition, "increased high-speed bandwidth" makes it possible to receive the same response times from centralized infrastructure at other sites.2)The cloud is becoming increasingly associated with small andmedium enterprises (SMEs) as in many cases they cannot justify or afford the large capital expenditure of traditional IT. SMEs also typically have less existing infrastructure, less bureaucracy, more flexibility, and smaller capital budgets forpurchasing in-house technology. Similarly, SMEs in emerging markets are typically unburdened by established legacyinfrastructures, thus reducing the complexity of deployingcloud solutionsⅥ. Origins of cloud computingIn 2006,Google engineer Christophe suggest Google CEO Eric Schmidt the idea of "cloud computing“ at the first time, under the support of Schmidt, Google rollout "Google 101 plan "and formally proposed the concept of “cloud ".Google's concept of “cloud computing” is a picturesque phrase, to describe Google's business model and computing technology architecture in a romantic way.therefore, cloud computing consists two levels of meaning, in commercial level, just the "cloud“; in the technical level is "computing",combined the cloud and computing to illustrate that Google is different with traditional software and hardware companies in business models and computing architecture. This is just a very beautiful and very romantic metaphor.Ⅶ. Brief IntroductionApache Hadoop is a framework for running applications on large cluster built of commodity hardware. The Hadoop framework transparently provides applications both reliability and data motion. Hadoop implements a computational paradigm named Map/Reduce, where the application is divided into many small fragments of work, each of which may be executed or re-executed on any node in the cluster. In addition, it provides a distributed (HDFS) that stores data on the compute nodes, providing very high aggregate bandwidth across the cluster. Both MapReduce and the Hadoop Distributed are designed so that node failures are automatically handled by the framework.Ⅷ. Two Important Technical1)HDFS: Hadoop Distributed (HDFS) is designed to reliably storevery large files across machines in a large cluster. It is inspired by the Google.2)MapReduce: MapReduce is a programming model for processing largedata sets with a parallel, distributed algorithm on a cluster.Ⅸ. 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