Comparing PaaS and IaaS

One of the most common questions I am asked when consulting or teaching Learning Tree’s Cloud Computing course is “What is the difference between Platform as a Service (PaaS) and Infrastructure as a Service (IaaS). This is an excellent question that the cloud computing vendors do little to help clarify.

Let’s consider IaaS first…
As the name suggests, what is provided here is an infrastructure delivered as a service. This includes hardware (servers, networks, load balancers etc) and software (operating systems, databases, application servers etc). The largest provider of IaaS is Amazon AWS and they have a wide variety of hardware and software combinations to choose from.

Now lets consider PaaS…
What we are gaining here is a platform as a service. This includes hardware (servers, networks, load balancers etc) and software (operating systems, databases, application servers etc). There are a number of PaaS providers including Google App Engine, Microsoft Azure and Salesforce.com’s Force.com.

Is the difference clear now ?
I thought not. On the surface the feature set of both IaaS and PaaS are the same but delving a little further a major difference is the amount of control a user has over the service. Take for example Microsoft Azure. Using Azure, the user has no control over the operating system, security features or the ability to install software applications – other than your own applications developed specifically for Azure. The same can be said for Google App Engine and Force.com. All operating system updates, versions, patches, security etc are controlled and implemented by the PaaS vendor.

Now considering IaaS. With IaaS, the user selects a configuration which defines server size, operating system, application software etc and then has complete responsibility for the maintenance of the system. If an operating system upgrade is required – its your responsibility. A security patch – its your responsibility. Want to install a new application or a database – feel free, its your server.

So in summary…
A major difference between IaaS and PaaS is the amount of control over the system available to users of the services. IaaS provides total control, PaaS typically provides no control. This also means virtually zero administration costs for PaaS whereas IaaS has administration costs similar to a traditional computing infrastructure.

There are many other differences between IaaS and PaaS of course. It is these kind of things that we investigate and evaluate as well as provide hands-on experience of in the Learning Tree Cloud Computing introduction course.

Chris Czarnecki

As cloud computing continues to make information technology headlines, vendors are aggressively promoting the many benefits it can provide organizations.  Our White Paper, Cloud Computing Promises: Fact of Fiction , addresses the claims and questions that are often raised in relation to cloud computing and provides a clear view of what the cloud can—and can’t—deliver in reality.

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