Hardware Environment

Modified

November 17, 2023

All CPUs on the cluster are a x86-64 compatible 1 processors architecture like AMD EPYC 2 and Intel XEON 3. A typical compute node hosts two multi-core Processors in a dual socket configuration. Nodes may have a variation in core count, available main memory or the local storage device capacity. Use Slurm commands to print an overview of the hardware resources like available CPU cores, and main memory (RAM).

>>> date ; sinfo -o "%20N %4c %6z %6m %5D %f"     
Wed Nov  8 09:38:35 CET 2023
NODELIST             CPUS S:C:T  MEMORY NODES AVAIL_FEATURES
lxbk[0719-0722]      128  2:32:2 257500 4     amd,epyc,7551,mi50
lxbk[1130-1265]      256  2:64:2 515000 136   amd,epyc,7713
lxbk[0724-1033]      96   2:24:2 191388 310   intel,xeon,gold6248r
lxbk[1034-1079]      256  8:16:2 103134 46    amd,epyc,7662
lxbk[1080-1129]      96   2:24:2 515451 50    amd,epyc,7413,mi100
lxbk[0717-0718]      128  2:32:2 257500 2     amd,epyc,7551,v100

Further details are described in the resource-allocation section. Nodes typically have a list of associated features to distinguish different CPU types. Some nodes support a GPU indicated in the feature list as well.

InfiniBand Network

The network connecting the cluster with its compute and storage nodes is build with an InfiniBand 4 interconnect. InfiniBand is a high-bandwidth and low-latency optimized High Performance Interconnect (HPI). It spreads network traffic across multiple parallel physical links (multipath) to scale the available bandwidth. The network topology is build like a fat-tree 5, with a 2 to 1 blocking factor on Virgo (over-subscription). This topology including its fault-tolerant routing allows optimal utilization of redundant network connections with high-throughput.

The application interface to InfiniBand is developed by the OpenFabrics Alliance (OFA) 6 and distributed as the open-source software OpenFabrics Enterprise Distribution (OFED). OFED includes a Linux kernel-level driver for channel-oriented RDMA and send/receive operations. This drive is accompanied by the kernel and an user-level Application Programming Interface (API).

In June 2023 the original network fabric based on InfiniBand FDR has been replaced with newer generation InfiniBand HDR equipment. The network is built from a combination of active and passive cables, both copper wires and optical fibers. Compute nodes are connected with so called splitter cables, optical breakout cables with a single port on the switch and to individual cables to edge nodes. Effectively this split the HDR 200Gbps bandwidth of a switch port into two 100Gbps uplinks for compute nodes.

GPU Accelerators

The Virgo cluster hosts a selection of nodes with GPUs for scientific computing. The majority of GPUs are AMD Radeon Instinct 7 cards, and a small set of Nvidia Tesla 8 for testing. Please refer to the GPUs example section.

GPUs (graphics processing units) in HPC offer a parallel architecture to speed up certain computing processes, especially those related to artificial intelligence (AI) and machine learning (ML) models. For suitable applications GPUs enable processing with higher efficiency and less power consumption, therefore at a lower cost. GPUs performance improves faster then CPUs driven by demand for the video game marked. Furthermore the specialised architectures simplifies scaling of transistors counts in GPUs.