[Copied from internal discussion]
Can you please clarify the answer to the question below?
I read that an HDFS cluster consists of many machines; one of these machines is designated as namenode and other machines act as datanodes.
Namenodes store metadata and datanodes store actual data. So I want to know whether they are services(programs) or actual machines.
Question: What best describes namenode or datanode?
Answer: Service that runs in background and listens on a network port