It handles faults by the process of replica creation. The replica of users data is created on different machines in the HDFS cluster. So whenever if any machine in the cluster goes down, then data can be accessed from other machine in which same copy of data was created. HDFS also maintains the replication factor by creating replica of data on other available machines in the cluster if suddenly one machine fails. To learn more about world’s most reliable storage layer follow this HDFS introductory guide.
Looking for HDFS Hands-on, follow these tutorials: Top 10 Useful Hdfs Commands Part-I