Architecting the Cloud: Design Decisions for Cloud Computing Service Models (SaaS, PaaS, and IaaS)

Chapter 2

Cloud Service Models

This is what our customers are asking for to take them to the next level and free them from the bondage of mainframe and client-server software.

—Marc Benioff, CEO, Salesforce.com

Choosing the right service model is a critical success factor for delivering cloud-based solutions. In order to choose the right service model or combination of service models, one must fully understand what each service model is and what responsibilities the cloud service providers assume versus the responsibilities the cloud service consumer assumes.

Infrastructure as a Service

There are three cloud service models: Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS). Each cloud service model provides a level of abstraction that reduces the efforts required by the service consumer to build and deploy systems. In a traditional on-premises data center, the IT team has to build and manage everything. Whether the team is building proprietary solutions from scratch or purchasing commercial software products, they have to install and manage one-to-many servers, develop and install the software, ensure that the proper levels of security are applied, apply patches routinely (operating system, firmware, application, database, and so on), and much more. Each cloud service model provides levels of abstraction and automation for these tasks, thus providing more agility to the cloud service consumers so they can focus more time on their ...