Cloud computing defined

I see two unrelated concepts called cloud computing.

The first one is related to grid computing, where parallelizable tasks are distributed to independent computing nodes and then aggregated to a consistent result. Frameworks like Hadoop, map-reduce algorithms, are an example of this approach.

The other paradigm is a virtual, private or public, data-computing center with an accessible API. You can model the environment in drag-and-drop-like fashion or, even more importantly, control it directly through a programmable API. You can, of course, run the grids in public or private clouds.

These paradigms also differ in their usage models. Grid computing is intended to be used by a few power users who need a considerable amount of computing power. On the other hand, in cloud computing, significantly more users access the machines with relatively low resource utilization.

While these two models are conceptually opposite, the underlying technology could be very similar. The first is often called platform as a service, and the latter, infrastructure as a service.

Adam Bien - Java Champion