HDFS is a software framework designed for Hadoop and it is one of the core components of Hadoop. HDFS is highly capable when compared to DBMS, say, it can store each bit of data in the form of three replicas by default. it's like, there is no way that HDFS can go down so easily. If you want to have a DBMS interface, then you have HBase and Pig environments for that. For more information, I suggest you follow this link.