Do you know your SaaS from your PaaS?

Do you know your SaaS from your PaaS?
By Charles Batchelor

Published: March 16 2011 17:29 | Last updated: March 16 2011 17:29

The “cloud,” as a term, has the virtue of simplicity. But burrow into the different types of cloud computing service on offer and you realise the techies have got hold of the dictionary. Infrastructure-as-a-service, platform-as-a-service and software-as-a-service are terms frequently used to describe the shapes the cloud can take.

“There are real differences, but there is also a degree of marketing spin,” says Rupert Chapman, a cloud specialist at PA Consulting. “They describe the levels of service on offer.”

Infrastructure-as-a-service (IaaS) involves the customer paying for off-site use of basic hardware and equipment – servers, network equipment, database storage from the provider. “I get access to very cheap shared machines and can put my own operating system and applications on top, so I have a degree of control,” says Mr Chapman.

Platform-as-a-service (PaaS) is the next level, with the customer renting both the machines and the operating systems that do the job. The customer does not need to understand the architecture of the platform or to carry out upgrades. At this level, customers can also develop and test their own applications.

Staff who are not programmers can try out applications to see how they work and if they are of value to customers and users. A credit-checking database could, for example, be used as a building block to construct a customer management application.

Software-as-a-service (SaaS) is the third layer in the cloud. Customers rent whatever applications they require – enterprise resource planning, customer relationship management and human resources are common business applications – and have only to log in to be able to use them.

“All I need is an internet browser and I can log in from home, the office or the coffee shop,” says Mr Chapman. “Everything is looked after by the cloud provider.”

SaaS is sometimes used as a catch-all phrase to mean “cloud computing”, but the purists insist the two terms are different. Cloud computing is the more general term used to cover the different levels of service available.

“Clients tend to forget about the labels,” says Mr Chapman. “These are terms that will stay in the IT world. Most business users don’t care and are probably turned off by them.”

“We prefer to call it IT-as-a-service,” says Michael Kogeler, director of cloud strategy at Microsoft International, which has launched Windows Azure as a cloud computing platform. “That’s more understandable.”

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