While listing various HDFS daemons, you should also talk about their roles in brief. Here is how you should answer this question:
Apache Hadoop HDFS Architecture follows a Master/Slave topology where a cluster comprises a single NameNode (Master node or daemon) and all the other nodes are DataNodes (Slave nodes or daemons). Following daemon runs in HDFS cluster:
NameNode: It is the master daemon that maintains and manages the data block present in the DataNodes.
DataNode: DataNodes are the slave nodes in HDFS. Unlike NameNode, DataNode is a commodity hardware, that is responsible of storing the data as blocks.
Secondary NameNode: The Secondary NameNode works concurrently with the primary NameNode as a helper daemon. It performs checkpointing.