Reprinted from: http://www.u1city.net/Article-538.html
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 tiers, namely 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.
What is IaaS, PAAs and SaaS and their differences