Apache Hadoop is an open source, Java-based programming framework that supports processing of large data sets in a distributed computing environment. It is part of the Apache project sponsored by the Apache Software Foundation.It is designed to scale up from a single server to thousands of machines, with a very high degree of fault tolerance. Rather than relying on high-end hardware, the resiliency of these clusters comes from the software's ability to detect and handle failures at the application layer.Hadoop is designed to be robust, in that your Big Data applications will continue to run even when individual servers or clusters fail.