Peng: The Classification of cloud computing

Cloud computing can be broadly grouped into three categories by service type: IaaS the infrastructure as a service, the platform as a service PAAs, and SaaS as a service, as shown in Figure 2.

Figure 2 Service types for cloud computing

IaaS encapsulates basic resources such as hardware devices into services for users, such as the flexible computing cloud EC2 and simple storage service S3 of Amazon Cloud computing AWS (Amazon WEB Services). In an IaaS environment, the user is equivalent to using bare metal and disk, so that it can run Windows, or it can run Linux, so you can almost do anything you want to do, but users have to think about how to get multiple machines working together. AWS provides an interface for exchanging messages between nodes Sqs simple Queue Service The biggest advantage of IaaS is that it allows users to dynamically request or release nodes, charging by usage. The number of servers running IaaS is as large as hundreds of thousands of, so users can assume that the resources they can apply for are almost limitless. The IaaS is shared by the public and therefore has a higher efficiency of resource utilization.

PAAs provides a level of abstraction for resources, providing a running environment for user applications, typically Google app Engine. Microsoft Windows Azure, the cloud computing operating system, can also be roughly grouped in this category. PAAs itself is responsible for dynamic expansion of resources and fault-tolerant management, and user applications do not have to consider the problem of coordination between nodes. At the same time, however, user autonomy has been reduced, and a specific programming environment must be used and followed by a specific programming model. This is a bit like MPI programming in high-performance Cluster computers and is only suitable for solving certain computational problems. Google app Engine, for example, only allows the use of Python and the Java language, the Web application framework called Django, and the Google App Engine SDK to develop online application services.

SaaS is more targeted and encapsulates some of the specific application functions as services, such as the online Customer Relationship management CRM (client relationship Management) service provided by Salesforce. SaaS does not provide a service for computing or storage resource types like PAAs, nor does it provide an environment for running user-defined applications, as IaaS does, and it provides only certain specialized service provisioning calls.

It should be noted that with the deepening development of cloud computing, different cloud computing solutions permeate each other, and the same product often spans more than two categories. For example, Amazon Web services started with PAAs, but the new flex-MapReduce service mimics Google's MapReduce, simple database services simpledb mimic Google's bigtable, Both belong to the PAAs category, and its new E-commerce services FPE and Devpay, as well as Web site access statistics Services Alexa Web Services, are part of the SaaS category.

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