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Aion Compute Nodes

Aion is a cluster of x86-64 AMD-based compute nodes. More precisely, Aion consists of 318 "regular" computational nodes named aion-[0001-0318] as follows:

Hostname (#Nodes) #cores type Processors RAM R_\text{peak}
aion-[0001-0318] (318) 40704 Regular Epyc 2 AMD Epyc ROME 7H12 @ 2.6 GHz [64c/280W] 256 GB 5.32 TF

Aion compute nodes compute nodes MUST be seen as 8 (virtual) processors of 16 cores each, even if physically the nodes are hosting 2 physical sockets of AMD Epyc ROME 7H12 processors having 64 cores each (total: 128 cores per node).

  • As will be highlighted in the slurm resource allocation, that means that targetting a full node utilization assumes that you use the following format attributes to your jobs: {sbatch|srun|si|salloc} [-N <N>] --ntasks-per-node <8n> --ntasks-per-socket <n> -c <thread> where
    • you want to ensure that <n>\times<thread>= 16 on aion
    • this will bring a total of <N>\times 8\times<n> tasks, each on <thread> threads
    • Ex: -N 2 --ntasks-per-node 32 --ntasks-per-socket 4 -c 4 (Total: 64 tasks)

Processor Performance

Each Aion node rely on an AMD Epyc Rome processor architecture which is binary compatible with the x86-64 architecture. Each processor has the following performance:

Processor Model #cores TDP(*) CPU Freq. R_\text{peak}
AMD Epyc ROME 7H12 64 280W 2.6 GHz 2.66 TF 2.13 TF

(*) The Thermal Design Power (TDP) represents the average power, in watts, the processor dissipates when operating at Base Frequency with all cores active under an Intel-defined, high-complexity workload.

Theoretical R_\text{peak} vs. Maximum R_\text{max} Performance for AMD Epyc

The AMD Epyc processors carry on 16 Double Precision (DP) ops/cycle. Thus the reported R_\text{peak} performance is computed as follows: R_\text{peak} = ops/cycle \times Freq. \times \#Cores

With regards the estimation of the Maximum Performance R_\text{max}, an efficiency factor of 80% is applied. It is computed from the expected performance runs during the HPL benchmark workload.

Regular Dual-CPU Nodes

These nodes are packaged within BullSequana X2410 AMD compute blades.

Each blade contains 3 dual-socket AMD Rome nodes side-by-side, connected to the BullSequana XH2000 local interconnect network through HDR100 ports which is done through a mezzanine board. The BullSequana AMD blade is built upon a cold plate which cools all components by direct contact, except DIMMS for which custom heat spreaders evacuate the heat to the cold plate -- see exploded view Characteristics of each blade and associated compute nodes are depicted in the below table

BullSequana X2410 AMD blade
Form Factor 1U blade comprising 3 compute nodes side-by-side
#Nodes per blade 3
Processors per node 2x AMD Epyc ROME 7H12 @ 2.6 GHz [64c/280W]
Architecture AMD SP3 Platform: 3x1 motherboard
Memory per node 256 GB DDR4 3200MT/s (8x16 GB DIMMs per socket, 16 DIMMs per node)
Network (per node) InfiniBand HDR100 single port mezzanine
Storage (per node) 1x 480 GB SSD
Power supply PSU shelves on top of XH2000 cabinet
Cooling Cooling by direct contact
Physical specs. (HxWxD) 44.45 x 600 x 540 mm

The four compute racks of Aion (one XH2000 Cell) holds a total of 106 blades i.e., 318 AMD Epyc compute nodes, totalling 40704 computing core -- see Aion configuration.

Last update: November 17, 2021