HDFS is the Hadoop Distributed File System. The HDFS design has aimed to achieve reliability and high-throughput access to application data. One of the most important design goals is the minimized cost of handling system faults caused by planned or unplanned outages.

HDFS has a master/slave architecture, where the master node exposes the NameNode service that manages files and their metadata, and the slave nodes expose DataNode services that manage block storage.

Why HDFS?

• HDFS is built to work on low-cost hardware
• HDFS has a simple design so it’s easy for developers to code and reason about it
• HDFS has built-in replication so it’s very reliable. It replicates every file 3 times across different slaves, so even if a slave node fails it can recover
• HDFS is high-throughput
• HDFS has good availability of data (if the DataNode is available)
• HDFS provides block-level storage (i.e., storing data in large blocks that can be spread over different nodes)
• HDFS has good performance
• HDFS is highly configurable and can be used for various applications