In the context of computer clusters what is the difference between the head-node of a cluster and the gateway to the cluster?
Many people seem to use the terms interchangeably so I am quite confused. Are they one and the same thing?
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The term "gateway" applies well to a node that carries live communication between nodes outside the cluster and nodes inside the cluster. This is a usual role in a networked cluster of workstations. It is not a usual role in a cluster of high-performance computing nodes.
The term "head node" applies well to a node that interprets requests from outside the cluster, directs, monitors, and manages the other nodes in the cluster as they work on those requests, gathers and combines the results, and finally sends the response. This is a usual role in a cluster of high-performance computing nodes.
A load-balanced web application, for a more complex example, may have one or more gateways to route communication to servers in the cluster, or one or more head nodes to distribute data and processing over servers in the cluster. It may even have both roles, either separated or combined.