Cloud-based infrastructure as a service (IaaS) is for renting storage and compute capacity from a service provider, delivered via an Internet connection. Similarly, software as a service (SaaS) is for accessing applications that are hosted in the cloud.
Platform as a service (PaaS) is sort of the like the red-headed stepchild between the two, providing an application development and hosting platform in the cloud. PaaS in many ways combines elements of infrastructure and software as a service.
But recently, Forrester researcher John Rymer, who closely tracks the PaaS market, says the lines between IaaS, SaaS and PaaS are beginning to blur.
Some of the leading IaaS companies, like Amazon Web Services, are adding PaaS-like features to their offerings. AWS has made it easier to deploy and scale applications in its cloud through services like its recently released OpsWorks, as well as Elastic Beanstalk and CloudFront, for example. SaaS pioneer Salesforce.com, meanwhile, is making a big push to promote its integrated PaaS offerings, Force.com and Heroku.
IaaS and SaaS are still strong markets in their own right, but increasingly providers in these areas are migrating toward the PaaS market as well. "These models are getting a good amount of usage," Rymer says.
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Rymer says the blurring of the lines between IaaS, SaaS and PaaS is driven by a couple of major factors. For one, vendors are looking to expand their service offerings to appeal to a wider customer base. Secondarily though, users are using the cloud in new ways, and looking for functionality from their providers. Rymer breaks PaaS users down into three buckets:
These are application developers who want an easy platform for developing applications without having to worry about configuring the infrastructure that the apps run on -- they just want to code in their programming language of choice -- Java, .Net, Ruby, Python, etc. A variety of pure-play PaaS vendors serve this market, including vendors like CloudBees, Engine Yard, Heroku and even Oracle, to an extent.
These are developers who like the idea of being able to build and deploy apps quickly, but they still want to have some control over the operations infrastructure, particularly for large-scale apps. "Usually when the apps get big, they want to tune the size of the VMs (virtual machines), storage and other components," he says. These are the ideal customers for IaaS providers looking to move up the stack into PaaS-like features.
These folks build applications, but they're not coders. These users are served well by tools offered from services like Force.com, which have intuitive visualization features, allowing users to build applications without coding in programming languages. Force.com is an example of a service that would allow this functionality.
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Many of these developer types require some sort of cloud platform that incorporates aspects of not just a pure IaaS, SaaS or PaaS, hence, the lines between these cloud options are converging. The application developers are creating opportunities for vendors to differentiate their services to appeal to the niches.
And it's not just the big-name brands of the industry, like Amazon Web Services and Salesforce.com making these moves to moderate their offerings closer to PaaS-like features.
Blue Box, a managed hosting and IaaS cloud provider that owns and operates its own data centers, has recently rolled out what could be thought of as IaaS+ service. Blue Box provides the infrastructure, and the customers bring their apps. It's targeted specifically at customers who have built customized applications on PaaS platforms like Heroku, Engine Yard, CloudBees or other public PaaS providers.
Pure-play PaaS vendors fall short in a number of areas, says Blue Box CEO Jesse Proudman. PaaS vendors tout their ability for developers to not worry about the underlying infrastructure their applications require. But Proudman says the more customers use a PaaS, the more control they're going to want over their infrastructure. Blue Box's IaaS+ model gives customers the ability to build their apps in the cloud on a PaaS, then migrate it to an infrastructure service provider, where they can dictate the configuration of the infrastructure. "Once you get to a large enough scale, the value prop of PaaS begins to fall apart," he says.
Microsoft's cloud service, Azure, combines elements of IaaS and PaaS too. Originally started as an application development platform, Microsoft then rolled out IaaS features like virtual machine and storage on demand. Now, Azure has both IaaS and PaaS functionality.
PaaS vendors would likely dispute claims that a PaaS alone cannot handle the needs of an application. But, the moves by IaaS and SaaS vendors to diversity their offerings to include more PaaS-like offerings reflect the evolving use cases by developers looking for that functionality.