Following are the steps followed by the block scanner when it detects a corrupted DataNode block- Whenever the block scanner comes across a block that is corrupted, the DataNode reports this particular block to the NameNode. The NameNode then processes the block and helps to create the replica of the same using the existing corrupted block. The system does not delete the corrupted block until the replication count of the newly created replicas matches with the replication factor which is 3 by default. This whole process helps HDFS in maintaining the integrity of the data during read operation performed by a client.