Cloud computing is the latest sea change affecting how we develop and deploy services and applications and fulfill the need for persistent information and database solutions. Database technology evolves even as new computing models emerge, inevitably raising questions about selecting the right database technology to match the new requirements.
The cloud is an elastic computing and data storage engine, a virtual network of servers, storage devices, and other computing resources. It’s a major milestone in on-demand or utility computing, the evolutionary progeny of computer timesharing, high-performance networks and grid computing. The computer timesharing industry that emerged four decades ago pioneered the model for on-demand computing and pay-per-use resource sharing of storage and applications. More recently Ian Foster and Carl Kesselman advanced the concept of the grid to make large-scale computing networks accessible via a service model. Like computer timesharing and the grid, cloud computing often requires persistent storage so open source projects and commercial companies have responded with data store and database solutions.
http://www.ddj.com/database/218900502
The New York Times project that created the TimesMachine, a web-accessible digital archive, is a prime example of a one-off cloud project requiring massively scalable computing.