For HPC applications that actually need low-latency coordination between nodes, the application code itself manages communication. The communication can't be better optimized by the OS.

If you have an embarrassingly parallel problem, it will run well on this machine but it will also be a waste of the machine's expensive design. Embarrassingly parallel problems run just as well on generic data center hardware. This machine is built for problems that only parallelize effectively with low-latency coordination between nodes. Such problems come up a lot in scientific/engineering simulations but are comparatively rare in general purpose computing environments. General purpose nodes in a cloud computing environment cannot run some of the harder problems this machine runs, at any price. For any non-trivial parallel computing job there comes a crossover point where adding more nodes makes the total time-to-solution longer rather than shorter. This point comes a lot sooner if you don't have dedicated high-bandwidth, low-latency interconnects between nodes.