Now days due to advancement of storage technology and computer technology, larger fraction of data is being maintained in digitized form. The same data is stored over and over again, consuming unnecessary storage space on the disc. Deduplication is ideal for highly redundant operations like backup, which requires repeatedly coping and storing the same data. Data deduplication is one of the most alive topics in storage because it enables companies to save a lot of money on storage costs. For cloud provider it is very helpful because you can deduplicate what you store. Due to reduction in cost it is being more popular. This paper will briefly describe Data Deduplication and give a comprehensive survey.