There’s quite a bit of confusion around the definitions of cloud computing.
Some users and consultants use the term to mean any software program that isn’t stored and used directly on site.
Yet others have latched onto a whole laundry list of acronyms that more accurately describe different types of cloud computing.
SaaS – Software As A Service
Essentially based on the concept of renting application functionality from a service provider rather than buying, installing and running software yourself. Offerings within this range from services such as Salesforce.com at one end, delivering the equivalent of a complete application suite, to players like MessageLabs at the other, whose services are designed to complement your operational infrastructure.
PaaS – Platform As A Service
Platform as a service (PaaS), which is all about providing, a platform in the cloud, upon which applications can be developed and executed. Players like Google, again Salesforce.com (this time with Force.com), and Microsoft (with Azure) exist in this space. Facilities provided include things like database management, security, workflow management, application serving, and so on.
IaaS – Infrastructure As A Service
Infrastructure as a service (IaaS). The proposition here is the offering of compute power and storage space on demand.
The difference between this and the other two categories of cloud is that the software that executes is essentially yours. In practical terms, the model is based on the same principles of virtualisation that we are all familiar with in the context of server partitioning or flexible storage. Rather than running a virtual image on a partition existing on a physical server in your data centre, you spin it up on a virtual machine that you have created in the cloud. Virtual disks can be created in a similar manner, to deal with the storage side of things.
For more details about cloud computing as well as to read an argument about whether this type of computing poses a danger to Internet Service Providers – read the full story at The Register.