HDFS (Hadoop Distributed File System) is one of the component of the Hadoop framework.
HDFS is a distributed file system, which means that it is using a cluster of servers to create a storage space.
HDFS can store any number of files. The files stored in the cluster are divided into data blocks and distributed among the different nodes of the HDFS cluster.
To guarantee data resilience, each data block is duplicated on several nodes (three by default).
Therefore, the file system is not affected if a node fails.