Service models in Cloud Computing


Cloud computing is based on Service model.

Categories of service model

The service models are categorized into three basic models:

1) Software-as-a-Service (SaaS)
2) Platform-as-a-Service (PaaS)
3) Infrastructure-as-a-Service (IaaS)

categories cloud computing

1) Software-as-a-Service (SaaS)

  • SaaS is known as 'On-Demand Software'.
  • It is a software distribution model. In this model, the applications are hosted by a cloud service provider and publicized to the customers over internet.
  • In SaaS, associated data and software are hosted centrally on the cloud server.
  • User can access SaaS by using a thin client through a web browser.
  • CRM, Office Suite, Email, games, etc. are the software applications which are provided as a service through Internet.
  • The companies like Google, Microsoft provide their applications as a service to the end users.
Advantages of SaaS
  • SaaS is easy to buy because the pricing of SaaS is based on monthly or annual fee and it allows the organizations to access business functionalities at a small cost, which is less than licensed applications.
  • SaaS needed less hardware, because the software is hosted remotely, hence organizations do not need to invest in additional hardware.
  • Less maintenance cost is required for SaaS and do not require special software or hardware versions.
Disadvantages of SaaS
  • SaaS applications are totally dependent on Internet connection. They are not usable without Internet connection.
  • It is difficult to switch amongst the SaaS vendors.

2) Platform-as-a-Service (PaaS)

  • PaaS is a programming platform for developers. This platform is generated for the programmers to create, test, run and manage the applications.
  • A developer can easily write the application and deploy it directly into PaaS layer.
  • PaaS gives the runtime environment for application development and deployment tools.
  • Google Apps Engine(GAE), Windows Azure, are the examples of PaaS.
Advantages of PaaS
  • PaaS is easier to develop. Developer can concentrate on the development and innovation without worrying about the infrastructure.
  • In PaaS, developer only requires a PC and an Internet connection to start building applications.
Disadvantages of PaaS
  • One developer can write the applications as per the platform provided by PaaS vendor hence the moving the application to another PaaS vendor is a problem.

3) Infrastructure-as-a-Service (IaaS)

  • IaaS is a way to deliver a cloud computing infrastructure like server, storage, network and operating system.
  • The customers can access these resources over cloud computing platform i.e Internet as an on-demand service.
  • In IaaS, you buy complete resources rather than purchasing server, software, datacenter space or network equipment.
  • IaaS was earlier called as Hardware as a Service(HaaS). It is a Cloud computing platform based model.
  • HaaS differs from IaaS in the way that users have the bare hardware on which they can deploy their own infrastructure using most appropriate software.
Advantages of IaaS
  • In IaaS, user can dynamically choose a CPU, memory storage configuration according to need.
  • Users can easily access the vast computing power available on IaaS Cloud platform.
Disadvantages of IaaS
  • IaaS cloud computing platform model is dependent on availability of Internet and virtualization services.