This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I would classify Hadoop as a "extreme record processing tool". Hadoop doesn't have transactional semantics which are offered by relational databases. It's really a batch-based system that allows you to work with large data volumes at scale.