1. Description of cloud computing
"Cloud" is essentially a network, in a narrow sense, cloud computing is a kind of resource of the network, the user can obtain the resources on the "cloud" at any time, according to the demand of use, and can be regarded as infinite extension, you can, as long as pay by the use of "cloud" like water works, we can always pick up water, and is not limited, according to their domestic water consumption, paying the waterworks can,
From a broad sense, cloud computing and information technology, software, Internet related a service, the Shared pool is called "cloud" computing resources, cloud computing together a lot of computing resources, through the software to realize automation management, need only a few people to participate in, can let the resources provided by the fast, that is to say, the computing power as a commodity, can circulate on the Internet, like water, electricity, gas, you can easily access, and the price is relatively cheap,
In short, cloud computing is not a kind of brand-new network technology, it is a new concept of network applications, the core of the cloud computing concept is centered on the Internet, the web site provides a quick and secure cloud computing services and data storage, let each people using the Internet can be used on the network computing resources and huge data center,
After the cloud computing is the Internet, the computer has a new innovation in the information era, cloud computing is a big leap in the information age, we make the coming age may be the age of cloud computing, although at present there are a lot about the definition of cloud computing, but overall, although cloud computing has many meanings, but in general, the basic meaning of cloud computing is consistent, namely, cloud computing has a strong extensibility and needs, can provide users with a whole new experience, is the core of the cloud computing can be a lot of computer resources to coordinate together, as a result, the user can access to the unlimited resources, through the network at the same time, access to resources is not limited by time and space,

2. The definition of cloud computing
For general users, cloud computing refers to through the network to on-demand, easy to extend the way to obtain the required services, namely anytime and anywhere as long as can connect to the Internet using a variety of services, the service can be IT and software, Internet related, also can be other services,

3. The classification of cloud computing
Cloud computing according to the type of service can be divided into infrastructure as a service (IaaS), platform as a service (PaaS), software as a service (SaaS), the function of each type and the service object, respectively is:
1) the cloud computing infrastructure as a service's biggest feature is that it's not like traditional server lease, rent entity specific server, it is rental server computing power and storage capacity, AWS will all Amazon computing center server computing power and storage capacity to integrate into a whole, and can be divided into a virtual instance, each instance represents a certain computing power and storage capacity, Amazon was the first company to sell infrastructure as a service company, Amazon elastic compute cloud of cloud computing platform can provide users or developers with a virtual cluster environment, small scale software developers to satisfy the demand of the cluster system, reduce the burden of maintenance, and solved the problem of the equipment idle, buy AWS cloud computing services company in these instances as a unit of measurement, virtualization technology is the key technology of IaaS,
2) Platform as a Service (Platform as a Service, abbreviation PaaS)
The transition layer, it is different from software as a service, platform as a service is for developers of cloud computing, the cloud computing's biggest feature is its own development environment, and provide development kit to developers, its representative has Google's GAE (Google App Engine), and domestic baidu BAE, sina SAE, platform as a service and software as a service can be mutual conversion between, if is the consumer, buying service Dropbox, the Dropbox is software as a service, if it is a developer, use Dropbox to provide development kit with the aid of Dropbox service to develop their own service, then the Dropbox itself is platform as a service, build on Dropbox is the developer of the service software as a service, the key technology of PaaS layer including parallel programming model, mass database, resource scheduling and monitoring technology architecture, very large distributed file systems such as distributed parallel computing platform technology,
3) Software as a Service SaaS (Software as a Service, abbreviation)
Is mainly responsible for providing users with software services, rent, software as a service is ordinary consumers can sense to cloud computing, its representatives have Dropbox, and domestic users familiar with baidu cloud, tencent micro cloud, the cloud computing's biggest feature is the consumers are not buying any entity product, but buy which has the function of equal to physical product service, SaaS areas represent the SaleForce,

4. Cloud computing and other forms of computing
1) with computing and distributed computing
According to the narrow definition, distributed computing is a problem to be solved is divided into several small problems, and then assigned to handle many computing system, finally the results by synthetically, the characteristics of distributed computing is to put the computing tasks to network more independent machine in parallel computing, major advantages:
Scarce resources can be Shared,
On multiple computers through distributed computing can load balance calculation,
Can put the program on the computer is most suited to running it,
At present more popular distributed projects mainly include:
seti@home: the search for extraterrestrial civilization,
folding@home: study on protein Folding and aggregation problem,
United Devices: look for effective drug against cancer,
Cloud computing including distributed computing characteristics mainly include:
Through the resource scheduling and combination to meet the user's resource requests,
Provides a unified single interface,
2) cloud computing and grid computing
It is mainly used for scientific computing

5. The key technology of cloud computing
Cloud computing can provide flexible services on demand, its architecture is roughly divided into three levels: the core service layer, service management, user access interface layer
(1) virtualization technology
Implementation of cloud computing is an important technical support for virtualization technology, virtualization technology to realize the logic of physical resource abstraction and unified said, created a virtual (not really), a variety of software and hardware resources can be formed a virtual resource pool, users and business application can more effectively use the resource pool, through virtualization technology can improve the utilization of resources, and can according to user requirements change, fast effective resource deployment,
(2) data storage technology
From safety, economy applicable perspective, distributed storage mode is undoubtedly the best choice of cloud storage, using multiple copies to store the same data or use a backup method, adopt parallel method on the service for the user to provide the required services, in addition, high transmission rate is also one of the features of cloud computing data storage technology, at present, using the services of the data storage technology with Google, Intel, etc.,
(3) the massive data management technology
Can cloud technology to deal with huge amounts of data, is the premise of use, data management technology must have the ability to efficient management of large amounts of data, at present, the data management technology in cloud computing system is mainly to Google's Big Table of data management technology and the development of the Hadoop open source data management module HBase,

6. Google cloud computing principle
Google's cloud computing infrastructure model includes four systems are independent of each other and together: Google File System distributed File System (GFS), a distributed lock mechanism is Chubby, Google development model simplified large scale distributed database BigTable (column type storage), and the characteristics of the true for Google apps graphs,
7. Amazon cloud services using the key value store,
S3 simple storage service (only provides data storage) is divided into temporary or permanent storage,