Article contributed by Amirreza Rastegari, Jon Shelley, Jithin Jose, Anshul Jain, Jyothi Venkatesh, Joe Greenseid, Fanny Ou, and Evan Burness

Azure has announced new HBv4-series and HX-series virtual machines (VMs) for high performance computing (HPC). This blog provides in-depth technical and performance information about these new VMs.

These VMs are powered by the latest technologies, including:

• 4^th Gen AMD EPYC CPUs (Genoa while in Preview, Genoa-X at General Availability in 1H2023)
• 800 GB/s of DDR5 memory bandwidth (STREAM TRIAD)
• 400 Gb/s NVIDIA Quantum-2 CX7 InfiniBand, the first on the public cloud
• 80 Gb/s Azure Accelerated Networking
• 3.6 TB local NVMe SSD providing 12 GB/s (read) and 7 GB/s (write) of storage bandwidth

HBv4 and HX – VM Size Details & Technical Specifications Overview

HBv4 and HX VMs are available in the following sizes with specifications as shown in Tables 1 and 2, respectively. Just like existing H- VMs, HBv4 and HX-series also include constrained cores VM sizes, enabling customers to choose a size along a spectrum of from maximum-performance-per-VM to maximum-performance-per-core.

HBv4-series VMs

HX-series VMs 

*Clock frequencies are based on non-AVX workload scenarios and are based on measured frequency delivery for workloads as captured by the Azure HPC team with AMD EPYC 7004-series processors and corresponding system firmware. Experienced clock frequency by a customer is a function of a variety of factors, including the coding and usage of a given application. Frequencies indicated above are not necessarily indicative of final clock frequencies for EPYC 7004-series processors.

For more information see the official documentation for HBv4-series and HX-series VMs.

Microbenchmark Performance

This section focuses on microbenchmarks that characterize performance of the memory subsystem and the InfiniBand network of the HBv4-series and HX series VMs.

STREAM – Memory Performance

Below in Figure 1, we share the results of running We ran the industry standard STREAM benchmark on HBv4/HX VMs. The STREAM benchmark was run using the following:

sudo ./run_stream_dynamic.py -nt 30 -t 176 -oca 0-175 -m 20000 -thp madvis

This returned a result of ~770 GB/s bandwidth for STREAM-TRIAD, which is over 2x greater than that provided from DRAM on HBv3 VMs (~350 GB/s STREAM-TRIAD) as documented here.

InfiniBand Perftests – Network Performance

HBv4 and HX VMs are equipped with latest NVIDIA Quantum-2 CX7 InfiniBand (NDR) interconnect. We ran the industry standard IB perftests test across two (2) HBv4-series VMs featuring 400 Gb/s (NDR) InfiniBand links. The IB bandwidth test was run using the following:

Unidirectional bandwidth:

numactl -c 0 ib_send_bw -aF -q 2

Bi-directional bandwidth:

numactl -c 0 ib_send_bw -aF -q 2 -b

Results of these tests are depicted in Figures 2 and 3, below.

As depicted above, HBv4/HX-series VMs achieve line-rate bandwidth performance (99% of peak) for both unidirectional and bi-directional tests.

Application Performance

This section will focus on characterizing performance of HBv4 and HX VMs on commonly run HPC applications. Performance comparisons are also provided across other HPC VMs offered on Azure, including:

• Azure HBv4/HX with 176 cores of AMD EPYC “Genoa” (HBv4 full specifications, HX full specifications)
• Azure HBv3 with 120 cores AMD EPYC “Milan-X” (full specifications)
• Azure HBv2 with 120 cores AMD EPYC “Rome” processors (full specifications)
• Azure HC with Intel 44 cores of Xeon Platinum “” (full specifications)

Note: HC-series represents a highly customer relevant comparison as the majority of HPC workloads, market-wide, still run largely or exclusively in on-premises datacenters and on infrastructure that is operated for, on average, between 4-5 years. Thus, it is important to include performance information of HPC technology that aligns to the full age spectrum that customers may be accustomed to using on-premises. Azure HC-series VMs well-represent the older end of that spectrum and also feature highly performant technologies like EDR InfiniBand, 1DPC DDR4 2666 MT/s memory, and Xeon Platinum 1^st Gen (“Skylake”) processors that dominated HPC customer investments and configuration choices during that period. As such, application performance comparisons below commonly use HC-series as a representative proxy for an approximately 4-year-old HPC optimized server.

Summary performance improvements with HBv4 and HX VMs compared to our most recent HPC VM offering, HBv3-series VMs are as follows:

• Up to 2.24x higher performance for CFD workloads
• Up to 5.3x higher performance for FEA workloads
• Up to 2.51x higher performance for weather simulation workloads
• Up to 2x higher performance for molecular dynamics workloads
• Up to 1.87x higher performance for rendering workloads
• Up to 2.45x higher performance for chemistry workloads

Computational Fluid Dynamics (CFD)

Ansys Fluent – version 2022 R2

The absolute values for the benchmark represented in Figure 4 are shared below:

In addition, we share here scale-up performance within a single VM:

The absolute values for the benchmark represented in Figure 5 are shared below:

Siemens Simcenter STAR-CCM+ – version 17.04.008

 

The absolute values for the benchmark represented in Figure 6 are shared below:

In addition, we share here scale-up performance within a single VM:

The absolute values for the benchmark represented in Figure 7 are shared below:

As we can see from the scale-up performance figures for Ansys Fluent and Siemens Simcenter STAR-CCM+, respectively, Constrained Cores HBv4/HX VMs provide significant benefits for customer workloads that may require lower core count due to commercial software licensing constraints. For example, looking at Table 4 for Ansys Fluent, the 96-core HBv4/HX VM size provides 73% of the performance of the 176-core VM size while requiring only 55% as many software licensed cores.

OpenFOAM – version 2012

The absolute values for the benchmark represented in Figure 8 are shared below:

Finite Element Analysis (FEA)

Altair RADIOSS – version 2022.1

The absolute values for the benchmark represented in Figure 9 are shared below:

MSC Nastran – version 2022.3

Note: for NASTRAN, the SOL108 medium benchmark was only tested on a HX-series VM because this VM type was created to support such large memory workloads. The larger memory footprint of HX-series (2x that of HBv4-series) allows the benchmark to run completely out of DRAM, which in turn provides additional performance speedup on top of that provided by the newer 4^th Gen EPYC CPUs and faster memory subsystem. As such, it would not be accurate to characterize the performance depicted below as “HBv4/HX” and we have instead marked it simply as “HX.”

The absolute values for the benchmark represented in Figure 10 are shared below:

Weather Simulation

WRF – version 4.2.2

The absolute values for the benchmark represented in Figure 11 are shared below:

Molecular Dynamics

NAMD – version 2.15

The absolute values for the benchmark represented in Figure 12 are shared below:

Rendering

V-Ray – version 5.02.00

The absolute values for the benchmark represented in Figure 13 are shared below:

Chemistry

CP2K – version 9.1

The absolute values for the benchmark represented in Figure 14 are shared below:

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