No, cluster network links are not nearly as elaborate as that, for the most part. The advent of high-speed crossbar links means that only the largest clusters need to even consider the network structure. You can get a 288 port Infiniband switch that provides full crossbar connectivity across all data paths. Only if you outgrow the largest available switch do you need to consider how to best link the multiple switches together. Generally this would involve minimizing the amount of IO that would need to be performed between the switches, which isn't always easy, or even possible.
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No, cluster network links are not nearly as elaborate as that, for the most part. The advent of high-speed crossbar links means that only the largest clusters need to even consider the network structure. You can get a 288 port Infiniband switch that provides full crossbar connectivity across all data paths. Only if you outgrow the largest available switch do you need to consider how to best link the multiple switches together. Generally this would involve minimizing the amount of IO that would need to be performed between the switches, which isn't always easy, or even possible.