HDFS : is a distributed file system that is well suited for the storage of large files. It\'s documentation states that it is not, however, a general purpose file system, and does not provide fast individual record lookups in files.
HBase: on the other hand, is built on top of HDFS and provides fast record lookups (and updates) for large tables. This can sometimes be a point of conceptual confusion. HBase internally puts your data in indexed "StoreFiles" that exist on HDFS for high-speed lookups.