Tuesday, June 28, 2011

Cloud Service Models - SaaS PaaS IaaS - Which One is for You?

Last week I was analyzing Google Analytics data of Techno-Pulse and found a few search keywords related to Cloud Service Models. It seems readers are looking for useful information on service models which can help them make decisions.  Though I’ve partially covered this topic in many posts, I’ll cover it here in a way that might help readers better understand and decide which cloud service model they should opt for.

SaaS Paas IaaS Techno-Toon

Cloud Service Models simply mean what type of services can be provided to customers. Different models cater to different kinds of requirements, and can achieve different business objectives. A simple search and you may find internet hits with dozens of Cloud * as a Service, where * can be replaced by any one of the following:

Desktop, Security, Data, Software, Platform, Infrastructure, IT, Testing, Hardware, Computing, Database, Storage etc.

All this is a bit confusing. As cloud computing is still evolving, the providers are free to innovate and offer various services, and there are no hard and fast rules governing these service offerings. So, let me simplify and put forward the most accepted type of Service Models, as defined by NIST (National institute of Standards and Technology, U.S. Department of Commerce)

NIST identifies 3 Cloud Service Models in its Special Publication 800-146. This document has been prepared for use by Federal agencies. It may be used by nongovernmental organizations on a voluntary basis and is not subject to copyright. For attributions check Reference Section of this article.

SPI Service Models

  • SaaS (Software as a Service)
  • PaaS (Platform as a Service)
  • IaaS (Infrastructure as a Service)

NIST further defines these services in detail, the summary of which is provided below, with my own interpretation.


Here the consumer is free of any worries and hassles related to the service. The Service Provider has very high administrative control on the application and is responsible for update, deployment, maintenance and security. The provider exercises final authority over the application. For example, Gmail is a SaaS where Google is the provider and we are consumers. We have very limited administrative and user level control over it, although there is a limited range of actions, such as enabling priority inbox, signatures, undo send mail, etc, that the consumer can initiate through settings.

The following figure illustrates the relative levels of control between the provider and the subscriber – SaaS Component Stack and Scope of Control  - borrowed from the NIST document.

SaaS Component Stack and Scope of Control

Who are SaaS Subscribers?

Apart from organizations and enterprises, SaaS subscribers/users can also be individuals like you and me. In most of the cases the usage fee is calculated based on the number of users. For example, Google Apps is free up to 10 email accounts, but it charges $5 per user per month for – Google Apps for Business (more than 10 users)

When/Why should you opt for a SaaS?

When you want to focus on your business rather than wasting your time in replacing broken pieces of hardware, managing IT infrastructure, and the most critical of them all - hiring and retaining your IT staff etc.

Which SaaS should you opt for?

  • Best use of SaaS is in productivity and collaboration apps in the cloud like Google Apps, Online Project Management like DeskAway, Zoho Mail, Chat, Docs, Project, Sheet, Writer etc.
  • CRM apps – Impel CRM, Salesforce.com, Microsoft Dynamics.
  • Cloud based Storage and Sharing services like Dropbox, Skydrive (windows live), Amazon S3, Google Docs, Box.net, Mozy.
  • SMEs/SMBs can opt for EazeWork (for HR, PayRoll and Sales)

Read More


In plain English, PaaS is a platform where software can be developed, tested and deployed, meaning the entire life cycle of a software can be operated on a PaaS. This service model is dedicated to application developers, testers, deployers and administrators. This service provides everything you need to develop a cloud SaaS application.

The following figure shows PaaS Component Stack and Scope of Control as defined by NIST:

PaaS Component Stack and Scope of Control

A PaaS typically includes the development environment, programming languages, compilers, testing tools and deployment mechanism. In some cases, like Google Apps Engine (GAE), the developers may download development environment and use them locally in the developer’s infrastructure, or the developer may access tools in the provider’s infrastructure through a browser.

Who are PaaS Subscribers?

ISV (Independent Software Vendors), IT Service providers or even individual developers who want to develop SaaS.

When/Why should you opt for a PaaS?

You focus only on developing the application, everything else will be taken care of by the platform.

Which PaaS should you opt for?

  • GAE is more popular with individual Java, Python developers.
  • Microsoft Windows Azure is targeting its pool of enterprise class users. ASP.Net (C#, VB.Net) developers will find easy to adopt it.
  • Amazon has also moved one stack up to offer its PaaS – Beanstalk (one more option for Java developers)
  • A few of the India based PaaS providers like OrangeScape and Wolf frameworks are making waves for their 5G visual PaaS. OrangeScape apps can run on all the major cloud platforms - Google App Engine, Microsoft Azure, IBM SmartCloud, Amazon EC2 or data center- without having to rewrite applications.
  • Engine Yard and Heroku are leading cloud PaaS for Ruby on Rails (RoR). Heroku (acquired by saleforce.com) is also a preferred PaaS for Facebook apps creation.
  • PHP developers can choose between PHP Fog and CloudControl.
  • For a multi-language application platform explore DotCloud.
  • India based Ozonetel Systems offers KooKoo PaaS for cloud telephony service.

Read More


Do you require virtual computers, cloud storage, network infrastructure components such as firewalls and configuration services? IaaS is what you should opt for. The System Administrators are the subscriber of this service. Usage fees are calculated per CPU hour, data GB stored per hour, network bandwidth consumed, network infrastructure used per hour, value added services used, e.g., monitoring, auto-scaling etc.

The following figure shows IaaS Component Stack and Scope of Control as defined by NIST:

IaaS Component Stack and Scope of Control

Who are IaaS Subscribers?

Are you aware of Farmville and Mafia Wars? Yes, these are the most popular Facebook games created by Zynga.com. It has more than 230 million monthly users run more than 12000 servers on Amazon AWS. When they launch a new game, they start with a few servers and then ramp up their capacity in real time.

To prevent the DDOS attack on its servers, the controversial Wikileaks was hosted on Amazon AWS. Now it seems it has moved back to a Swedish host.

Most important among the lot are SaaS and PaaS Players who are hosted with IaaS providers.

India based online ticketing service redBus. For details read the Case study What  IRCTC can learn from redBus cloud implementation.

When/Why should you opt for an IaaS?

Very useful for startup companies who don’t know how successful their newly launched application/website will be.

You have the choice of multiple Operating System, Platforms, Databases and Content Delivery Network (CDN) – all in one place.

Note - Due to economic reasons currently it may not be advisable to host a static website with less than 10,000 visits/month on an IaaS. This may cost you around $18/month on Amazon AWS (Source:  An AWS presentation, Jan 2011)

Which IaaS should you opt for?

Amzon is the pioneer of IaaS. Other leading providers are Rackspace, GoGrid, Joyent, Rightscale and Terremark (bought by Verizon)

For India based IaaS – explore the following providers:

  • NetMagic Solutions
  • InstaCompute (from Tata Communications)

Read More

Are you still thinking which service model is right for you? Feel free to share your query in the comment section.


NIST Cloud Computing Synopsis and Recommendations - Special Publication 800-146


  1. Unfortunately the view at article is over simplified. In many cases same service can be SaaS and PaaS at the same time. E.g. SalesForce has properties from both sides. It has SaaS type of application with Chatter but at the same time it is also providing development platform. Same is with spreadsheet at Google Docs. I can develop applications with with (combined with Google Apps), but it's also SaaS at the same time.

  2. @Teme: "Salesforce CRM" is a pure SaaS. The PaaS offered by Salesforce.com is known as "Force.com". Google's PaaS is known as GAE.

  3. This article is very much useful as I think. The description is too good. I was looking for such article. I have read a similar article here "http://www.techyv.com/article/term-iaas-stands-infrastructure-service" which is very helpful also.

  4. I would like to know where I can find journal articles about cloud computing on the internet (Journals Libraries). I need published articles on a journal to be used in my M.Phil. research. Thanks in advance

  5. Very good article for beginners like myself

  6. Thanks for the nice article~!

    but still I'm a little confused...

    so, I have a question for you.

    What do you think about Apple's iCloud?

    Is Apple's iCloud SaaS?, PaaS? or IaaS?

  7. iCloud is a SaaS. Also note, Cloud is evolving & with time the thin line between these 3 stacks/models are disappearing. For example, Windows Azure is a PaaS but is gradually evolving towards an IaaS.

    The following articles about iCloud may help you:



  8. Thank you for you information.
    I need your guidness.

    I am intrested in cloud computing and took seminars about basic cloud concepts.

    I want to learn about the cloud computing in depth
    i want to know how they develop the cloud environment and how the deploy software and every thing about it.

    so can you please tell me where we can learn cloud computing

    is there any international certificcations or any thing to learn . please guide me.


  9. www.appreef.com is a addition to this. AppReef L.L.C., a technology startup company founded in 2010 with a mission to develop Cloud Computing Platform-as-a-Service (PaaS) for Enterprises and Small Businesses to eliminate the need for back-end IT infrastructure and in-house custom web-based applications. AppReef PaaS enables rapid development and deployment of fully functional web-based applications with customizable user interfaces all via web browser.

  10. Great post..
    Thank you for sharing..
    clears all doubts related to the services of Cloud Computing.

  11. Hi. Can you tell me further about SaaS and difference of IaaS & SaaS?

    Here i read about the difference between IaaS PaaS & SaaS. What do you think of it?