Three modes of service for cloud computing: Iaas,paas and SaaS

Cloud Services "Now it's almost a household word. If you don't know the difference between PAAs, IaaS, and SaaS, then there's nothing, because a lot of people don't really know.
"Cloud" is actually a metaphor of the internet, "cloud computing" is actually using the Internet to access storage or run on the remote server side of the application, data, or services.
Any company that uses an Internet-based approach to compute, store, and develop can technically be called a cloud-engaged company. However, not all cloud companies are the same. Not all of us are CTO, so sometimes it may be a headache to see some of the words behind cloud technology.

The cloud is also layered

Any company that provides its services on the internet can be called a cloud computing company. In fact, cloud computing is divided into several layers, respectively, infrastructure (infrastructure)-as-a-service,platform (platform)-as-a-service,software (software)-as-a-service. Infrastructure at the bottom, platform in the middle, software at the top. Other "soft" layers can be added on top of these layers.

Iaas:infrastructure-as-a-service (infrastructure as a service)

The first layer is called IaaS, sometimes called Hardware-as-a-service, and a few years ago if you want to run some business applications in your office or on your company's website, you need to buy servers or other high-level hardware to control your local applications and get your business up and running.
But with IaaS now, you can outsource your hardware to other places. IaaS will provide off-site servers, storage and network hardware that you can rent. Save on maintenance costs and office space, companies can use these hardware at any time to run their applications.
Some large IaaS companies include Amazon, Microsoft, VMWare, Rackspace and Red Hat. However, these companies have their own expertise, such as Amazon and Microsoft provide you with not only IaaS, they will also rent their computing power to you to host your site.

Paas:platform-as-a-service (Platform as a service)

The second layer is called PAAs, which is sometimes called middleware. All the development of your company can be done at this level, saving time and resources.
PAAs offers a variety of solutions for developing and distributing applications on the web, such as virtual servers and operating systems. This saves you money on the hardware and makes it easier to collaborate between decentralized studios. Web application management, application design, application virtual hosting, storage, security and application development collaboration tools, etc.
Some large PAAs providers have Google App engine,microsoft azure,force.com,heroku,engine Yard. Recent companies have Appfog, Mendix and standing Cloud

Saas:software-as-a-service (software as a service)

The third layer is called SaaS. This layer is a layer of daily contact with your life, most of which is accessed through a Web browser. Any application on a remote server can be run over the network, which is SaaS.
The services you consume are completely accessible from websites such as Netflix, MOG, Google Apps, Box.net, Dropbox or Apple's icloud. Although these Web services are used for business and entertainment or both, this is part of cloud technology.
Some of the SaaS applications used for business include Crm,adp,workday and SuccessFactors of Citrix's Gotomeeting,cisco Webex,salesforce.

Comparison between IaaS and PAAs

The main role of PAAs is to provide a development and operational platform as a service to the user, and the primary role of IaaS is to provide virtual machines or other resources as a service to the user. Next, the PAAs and IaaS will be compared in seven ways:

    1) Development environment: PAAs basically gives developers a complete set of development and test environments, including the IDE, while IaaS users are mostly familiar with the development environment before But because of the previous development environment in the integration with the cloud is relatively inadequate, so it is not very convenient to use.
    2) supported applications: Because IaaS primarily provides virtual machines, and common virtual functions support multiple operating systems, the scope of IAAS-supported applications is extensive. But it's not easy to make an app run on a PAAs platform, because not only is it necessary to ensure that the application is based on the language supported by the platform, but also to make sure that the application can only invoke the APIs supported by the platform, and if the application calls an API that the platform does not support, Then you need to make changes to the application.
3) Open standards: While many of the IaaS platforms have some private functionality, the existence of protocols such as OVF makes it a steady step on both sides of the platform and avoiding vendor lock-in. The PAAs platform is not optimistic because both Google's app Engine and Salesforce's force.com have some proprietary APIs.
    4) Scalability: The PAAs platform automatically adjusts resources to help applications running on it to better respond to bursts of traffic. The IaaS platform requires developers to manually adjust the resources to cope.
    5) Consolidation rate and economy: PAAs platform consolidation rate is very high, for example, the PAAs representative of Google App engine can host thousands of applications on a single server, The average IaaS platform's integration rate is no more than 100, and generally around 10, making IaaS less economical than PAAs.
    6) Billing and regulation: Because the PAAs platform is both billing and regulatory, it achieves the same level of operating system as the IaaS platform, such as CPU and memory usage, and can be applied, for example, The application's response time (Response times) or the amount of transactions consumed by the application will increase the accuracy of billing and management.
    7) Learning Difficulty: Because the development and management of applications on the IaaS is relatively close to the existing approach, while PAAs development may require learning a new language or a new framework, IaaS learning is less difficult.

	Paas	Iaas
Development environment	Perfect	Ordinary
Supported applications	Finite	Wide
Versatility	Lack	Slightly better
Scalability	Auto Scaling	Manual Scaling
Consolidation rate and economy	High integration rate, more economical	Low integration rate
Billing and regulation	Fine	Simple
Learning Difficulty	Slightly difficult	Low

Table 1. Comparison between PAAs and IaaS

PK of the Future

In today's cloud computing environment, IaaS is very mainstream, whether Amazon EC2 or Linode or joyent, and so on, but with Google's app Engine, The force.com of Salesforce is also the launch of a PAAs platform such as Microsoft's Windows Azure, making PAAs even more emerging. When it comes to the future of both, and especially the competitive relationship between the two, I personally think that in the short term, because of the advantages of the IaaS model in terms of both supported applications and learning difficulties, IaaS will become the developer's first choice in the short term, but in the long run, Because the high integration rate of the PAAs model brings economic benefits, it will replace IaaS as a developer's "favorite" if PAAs solves challenges such as versatility and supported applications.

http://blog.csdn.net/hjxgood/article/details/18363789

Three modes of service for cloud computing: Iaas,paas and SaaS