As technology advances,we are surrounded by big data,they are omnipresent. In every minute,Facebook users share nearly 2.5 million pieces of content. YouTube users upload 72 hours of new video content.So how can we do with such huge data? Apache Hadoop is an open source software framework for storage and large scale processing of data-sets on clusters of commodity hardware.By using MapReduce in Hadoop,we can acess data and mining it easily