The Computer Weekly guide to Cloud Computing

Bob Tarzey

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The difference between Saas, Paas and Iaas

The lowest level is infrastructure-as-a-service (IaaS). This is where pre-configured hardware is provided via a virtualised interface or hypervisor. There is no high level infrastructure software provided such as an operating system, this must be provided by the buyer embedded with their own virtual applications. Platform as a service (PaaS) goes a stage further and includes the operating environment included the operating system and application services. PaaS suits organisations that are committed to a given development environment for a given application but like the idea of someone else maintaining the deployment platform for them. Saas offers fully functional applications on-demand to provide specific services such as email management, CRM, ERP, web conferencing and an increasingly wide range of other applications.

Cloud computing is changing the way IT deparrtments buy IT. Businesses have a range of paths to the cloud, including infrastructure, platforms and applications that are available from cloud providers as online services. Many people may be confused by the range of offerings and the terminology used to describe them and will be unsure of the risk and benefits. This gallery, written for Computer Weekly, by Bob Tarzey of Quocirca aims to provide further insight.

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