There are a few options for backup and recovery. As s.singh points out, data replication is not DR.
HDFS supports snapshotting. This can be used to prevent user errors, recover files, etc. That being said, this isn't DR in the event of a total failure of the Hadoop cluster. (http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-hdfs/HdfsSnapshots.html)
Your best bet is keeping off-site backups. This can be to another Hadoop cluster, S3, etc and can be performed using distcp. (http://hadoop.apache.org/docs/stable1/distcp2.html), (https://wiki.apache.org/hadoop/AmazonS3)
Here is a Slideshare by Cloudera discussing DR (http://www.slideshare.net/cloudera/hadoop-backup-and-disaster-recovery)