Cloud Computing – How It Works?

IBM Cloud Computing
IBM Cloud Computing (Photo credit:

What is Cloud Computing?

Whenever this questions is asked, everybody has a different definition of CLOUD COMPUTING.

Image via : wikipedia

According to Wikipedia

“Cloud Computing is a colloquial expression used to describe a variety of different types of computing concepts that involve a large number of computers that are connected through a real-time communication network (typically the Internet).”

According to AWS

“Cloud Computing refers to applications and services that run on a distributed networks using virtualized resources and accessed by common Internet protocols and networking standards.”

In a simpler words, CLOUD COMPUTING is an internet based computing where various services such as APPLICATIONS, SERVERS, STORAGE, etc are available through internet. With the technology of cloud computing we can now STORE, ACCESS and PROCESS DATA and APPLICATIONS over the internet instead of our system’s hard drives.

Source : (AWS)

Source : (SaleForce)

Architectural Layers of Cloud Computing

  1. Infrastructure-as-a-Service (IaaS)
  2. Platform-as-a-Service (PaaS)
  3. Software-as-a-Service (SaaS)
Image via : CIO Research Center

Infrastructure-as-a-Service (IaaS)

Infrastructure as a Service (IaaS), delivers basic storage and compute capabilities as standardized services over the network. Servers, storage systems, switches, routers, and other systems are pooled and made available to handle workloads that range from application components to high-performance computing applications. In this the service provider is the owner of the equipment and is responsible for configuring , running and maintaining it. The client, on the other hand, pays on a per-use basis.

Examples of IaaS providers : Amazon EC2, Google Compute Engine, HP Cloud, Joyent, Linode, NaviSite, Rackspace, and ReadySpace Cloud Services.

Platform-as-a-Service (PaaS)

Platform as a Service (PaaS) encapsulates a layer of software and provides it as a service that can be used to build higher-level services.It provides application execution services like application runtime, storage, and integration. In this  the provider provides the servers, networks, storage and other services. On the other hand, the consumer controls software deployment and configuration settings. There are at least two perspectives on PaaS depending on the perspective of the producer or consumer of the services :

  1. Someone producing PaaS might produce a platform by integrating an OS, middleware, application software, and even a development environment that is then provided to a customer as a service.

  2. Someone using PaaS would see an encapsulated service that is presented to them through an API. The customer interacts with the platform through the API, and the platform does what is necessary to manage and scale itself to provide a given level of service.

Examples PaaS AWS Elastic Beanstalk, Cloud Foundry, Heroku,, EngineYard, Mendix, OpenShift, Google App Engine,AppScale, Windows Azure Cloud Services, OrangeScape and Jelastic.

Software-as-a-Service (SaaS)

Software as a Service (SaaS) features a complete application offered as a service on demand. A single instance of the software runs on the cloud and services multiple end users or client organizations. It provides business processes and applications, including CRM, e-mails, collaboration, etc. SaaS is also knows as “on-demand software” and is usually priced on a pay-per-use basis. The most widely known example of SaaS is, though many other examples have come to market, including the Google Apps offering of basic business services including email and word processing.

Examples of SaaS Google Apps, Microsoft Office 365, Petrosoft, Onlive, GT Nexus, Marketo, Casengo, TradeCard, Salesforce and CallidusCloud.

Infrastructure or Deployment Models of Cloud Computing

  1. Public Clouds
  2. Private Clouds
  3. Hybrid Clouds


A public cloud provides services to multiple customers, and is typically deployed at a collocation facility. Public clouds are run by third parties, and applications from different customers are likely to be mixed together on the cloud’s servers, storage systems, and networks. Public clouds are most often hosted away from customer premises, and they provide a way to reduce customer risk and cost by providing a flexible, even temporary extension to enterprise infrastructure.



Private clouds may be hosted at a collocation facility or in an enterprise data center. They may be supported by the company, by a cloud provider, or by a third-party such as an outsourcing firm. Private clouds are built for the exclusive use of one client, providing the utmost control over data, security, and quality of service.



Hybrid clouds combine both public and private cloud models. They can help to provide on-demand, externally provisioned scale. If the data is small, or the application is stateless, a hybrid cloud can be much more successful than if large amounts of data must be transferred into a public cloud for a small amount of processing. Hybrid clouds combine both public and private cloud models, and they can be particularly effective when both types of cloud are located in the same facility.

Images Source : wikipedia , CIO Research Center
Videos Source : AWS, SaleForce

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