Two Ways to Keep Files in Sync Between Alluxio and HDFS

Alluxio provides a distributed data access layer for applications like Spark or Presto to access different underlying file system (or UFS) through a single API in a unified file system namespace. If users only interact with the files in the UFS through Alluxio, since Alluxio has knowledge of any changes the client makes to the UFS, it will keep Alluxio namespace in sync with the UFS namespace.