A really interesting discussion has been going on in the LinkedIn IT Architect group. If you aren't a member of the group, I highly recommend you join. The question that fired off the discussion was, "Is 'the cloud' just another name for a hosted / out-sourced (web application) service? If not, what sets it apart? How is it different?" Considering the current work I've done developing a cloud product, I found the responses informative. Below are a few of the responses I really liked.
"Saving money is great but having the agility to deploy a service JiT and win incomes when targetted is more important. The real benefits of the cloud are not in optimization of hardware ressources but in the elasticity it add to TTM and run processes."
"I'm in the midst of my second Amazon deployment. In my experience their offering is more sophisticated and powerful than others. Rather than just letting you rent virtualized servers, they provide what I call "Architecture as a Service". AaaS is a set of building blocks needed to deploy a highly scalable, highly available online system, with interesting architectural components such as asynchronous messaging, transparently replicated storage, geographically distributed load balancing, and so on."
"NIST defines the Cloud out quite nicely:
Five Essential Characteristics
- On-demand self service –Users are able to provision, monitor and manage computing
resources as needed without the help of human administrators
- Broad network access – Computing services are delivered over standard networks and
- Rapid elasticity – IT resources are able to scale out and in quickly and on an as needed basis
- Resource pooling – IT resources are shared across multiple applications and tenants in a
- Measured service – IT resource utilization is tracked for each application and tenant, typically for public cloud billing or private cloud chargeback
"Virtualization changes the computing paradigm significantly. It introduces a paradigm shift in business models."
"Here is a a good practical read with excellent comparative data - D. Ruest and N. Ruest (2009), Virtualization: A Beginner's Guide, McGrawHill, ISBN: 978-0-07-161401-6"