  Novel low-diameter network topologies such as Slim Fly (SF) offer significant
cost and power advantages over the established Fat Tree, Clos, or Dragonfly. To
spearhead the adoption of low-diameter networks, we design, implement, deploy,
and evaluate the first real-world SF installation. We focus on deployment,
management, and operational aspects of our test cluster with 200 servers and
carefully analyze performance. We demonstrate techniques for simple cabling and
cabling validation as well as a novel high-performance routing architecture for
InfiniBand-based low-diameter topologies. Our real-world benchmarks show SF's
strong performance for many modern workloads such as deep neural network
training, graph analytics, or linear algebra kernels. SF outperforms
non-blocking Fat Trees in scalability while offering comparable or better
performance and lower cost for large network sizes. Our work can facilitate
deploying SF while the associated (open-source) routing architecture is fully
portable and applicable to accelerate any low-diameter interconnect.
