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All of the compute and login nodes of Karolina are interconnected through an InfiniBand HDR 200Gbps network and a gigabit ethernet network.

The compute network is configured as a non-blocking Fat Tree which consists of 60 x 40-ports Mellanox Quantum™ HDR switches (40 Leaf HDR switches and 20 Spine HDR switches).

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Compute nodes and the service infrastructure is connected by the HDR100 technology that allows one 200Gbps HDR port (aggregation 4x 50Gbps) divided into 2 HDR100 ports with 100Gbps (2x 50Gbps) bandwidth. The cabling between the L1 and L2 layer is realized by HDR cabling, connecting the end devices is realized by so called Y or splitter cable (1x HDR200 - 2x HDR100).

The compute network has the following parameters

  • 100Gbps
  • Latencies less than 10 microseconds (0.6μs end-to-end, <90ns switch hop)
  • Adaptive routing support
  • MPI communication support
  • IP protocol support (IPoIB)
  • Support for SCRATCH Data Storage and NVMe over Fabric Data Storage.

Mellanox Quantum™ QM8790 40-Ports Switch

Mellanox provides the world’s smartest switch, enabling in-network computing through the Co-Design Scalable Hierarchical Aggregation and Reduction Protocol (SHARP)™ technology. QM8790 has the highest fabric performance available in the market with up to 16Tb/s of non-blocking bandwidth with sub-130ns port-to-port latency.


  • 40 x HDR200 200Gb/s ports in a 1U switch
  • 80 x HDR100 100Gb/s ports (using splitter cables)
  • 16Tb/s aggregate switch throughput
  • Sub-130ns switch latency – Optimized design

Optimized Design

  • 1+1 redundant & hot-swappable power
  • N+1 redundant & hot-swappable fans
  • 80 gold+ and energy star certified power supplies

Advanced Design

  • Adaptive routing
  • Congestion control
  • Collective offloads (Mellanox SHARP™ technology)
  • VL mapping (VL2VL)