Hadoop is an open source software project initially developed by Google as a means of extracting search results from large amounts of unstructured data, such as data found on the web. It was used by many large corporations where networked scalability, cost effectiveness and fault tolerance were critical to their business models. Companies such as Google, Yahoo, American Airlines, IBM and Twitter all used Hadoop, and it could be scaled from a single server to thousands. With Hadoop different types of data could be seamlessly integrated and Hadoop could redirect work to another system if a node failed in the cluster.