High performance compute VM sizes

Azure H-series virtual machines (VMs) are designed to deliver leadership-class performance, MPI scalability, and cost efficiency for a variety of real-world HPC workloads.

HBv2-series VMs feature 200 Gb/sec Mellanox HDR InfiniBand, while both HB and HC-series VMs feature 100 Gb/sec Mellanox EDR InfiniBand. Each of these VM types are connected in a non-blocking fat tree for optimized and consistent RDMA performance. HBv2 VMs support Adaptive Routing and the Dynamic Connected Transport (DCT, in additional to standard RC and UD transports). These features enhance application performance, scalability, and consistency, and usage of them is strongly recommended.

HB-series VMs are optimized for applications driven by memory bandwidth, such as fluid dynamics, explicit finite element analysis, and weather modeling. HB VMs feature 60 AMD EPYC 7551 processor cores, 4 GB of RAM per CPU core, and no hyperthreading. The AMD EPYC platform provides more than 260 GB/sec of memory bandwidth.

HC-series VMs are optimized for applications driven by dense computation, such as implicit finite element analysis, molecular dynamics, and computational chemistry. HC VMs feature 44 Intel Xeon Platinum 8168 processor cores, 8 GB of RAM per CPU core, and no hyperthreading. The Intel Xeon Platinum platform supports Intel’s rich ecosystem of software tools such as the Intel Math Kernel Library.

H-series VMs are optimized for applications driven by high CPU frequencies or large memory per core requirements. H-series VMs feature 8 or 16 Intel Xeon E5 2667 v3 processor cores, 7 or 14 GB of RAM per CPU core, and no hyperthreading. H-series features 56 Gb/sec Mellanox FDR InfiniBand in a non-blocking fat tree configuration for consistent RDMA performance. H-series VMs support Intel MPI 5.x and MS-MPI.

Deployment considerations

  • Azure subscription – To deploy more than a few compute-intensive instances, consider a pay-as-you-go subscription or other purchase options. If you're using an Azure free account, you can use only a limited number of Azure compute cores.

  • Pricing and availability - These VM sizes are offered only in the Standard pricing tier. Check Products available by region for availability in Azure regions.

  • Cores quota – You might need to increase the cores quota in your Azure subscription from the default value. Your subscription might also limit the number of cores you can deploy in certain VM size families, including the H-series. To request a quota increase, open an online customer support request at no charge. (Default limits may vary depending on your subscription category.)


    Contact Azure Support if you have large-scale capacity needs. Azure quotas are credit limits, not capacity guarantees. Regardless of your quota, you are only charged for cores that you use.

  • Virtual network – An Azure virtual network is not required to use the compute-intensive instances. However, for many deployments you need at least a cloud-based Azure virtual network, or a site-to-site connection if you need to access on-premises resources. When needed, create a new virtual network to deploy the instances. Adding compute-intensive VMs to a virtual network in an affinity group is not supported.

  • Resizing – Because of their specialized hardware, you can only resize compute-intensive instances within the same size family (H-series or compute-intensive A-series). For example, you can only resize an H-series VM from one H-series size to another. In addition, resizing from a non-compute-intensive size to a compute-intensive size is not supported.

RDMA-capable instances

A subset of the compute-intensive instances (A8, A9, H16r, H16mr, HB and HC) feature a network interface for remote direct memory access (RDMA) connectivity. Selected N-series sizes designated with 'r' such as the NC24rs configurations (NC24rs_v2 and NC24rs_v3) are also RDMA-capable. This interface is in addition to the standard Azure network interface available to other VM sizes.

This interface allows the RDMA-capable instances to communicate over an InfiniBand (IB) network, operating at EDR rates for HB, HC, FDR rates for H16r, H16mr, and RDMA-capable N-series virtual machines, and QDR rates for A8 and A9 virtual machines. These RDMA capabilities can boost the scalability and performance of certain Message Passing Interface (MPI) applications. For more information on speed, see the details in the tables on this page.


In Azure, IP over IB is only supported on the SR-IOV enabled VMs (SR-IOV for InfiniBand, currently HB and HC). RDMA over IB is supported for all RDMA-capable instances.

  • Operating system - Windows Server 2016 on all the above HPC series VMs. Windows Server 2012 R2, Windows Server 2012 are also supported on the non-SR-IOV enabled VMs (hence excluding HB and HC).

  • MPI - The SR-IOV enabled VM sizes on Azure (HB, HC) allow almost any flavor of MPI to be used with Mellanox OFED. On non-SR-IOV enabled VMs, supported MPI implementations use the Microsoft Network Direct (ND) interface to communicate between instances. Hence, only Microsoft MPI (MS-MPI) 2012 R2 or later and Intel MPI 5.x versions are supported. Later versions (2017, 2018) of the Intel MPI runtime library may or may not be compatible with the Azure RDMA drivers.

  • InfiniBandDriverWindows VM extension - On RDMA-capable VMs, add the InfiniBandDriverWindows extension to enable InfiniBand. This Windows VM extension installs Windows Network Direct drivers (on non-SR-IOV VMs) or Mellanox OFED drivers (on SR-IOV VMs) for RDMA connectivity. In certain deployments of A8 and A9 instances, the HpcVmDrivers extension is added automatically. Note that the HpcVmDrivers VM extension is being deprecated; it will not be updated. To add the VM extension to a VM, you can use Azure PowerShell cmdlets.

    The following command installs the latest version 1.0 InfiniBandDriverWindows extension on an existing RDMA-capable VM named myVM deployed in the resource group named myResourceGroup in the West US region:

    Set-AzVMExtension -ResourceGroupName "myResourceGroup" -Location "westus" -VMName "myVM" -ExtensionName "InfiniBandDriverWindows" -Publisher "Microsoft.HpcCompute" -Type "InfiniBandDriverWindows" -TypeHandlerVersion "1.0"

    Alternatively, VM extensions can be included in Azure Resource Manager templates for easy deployment, with the following JSON element:

    "publisher": "Microsoft.HpcCompute",
    "type": "InfiniBandDriverWindows",
    "typeHandlerVersion": "1.0",

    The following command installs the latest version 1.0 InfiniBandDriverWindows extension on all RDMA-capable VMs in an existing VM scale set named myVMSS deployed in the resource group named myResourceGroup:

    $VMSS = Get-AzVmss -ResourceGroupName "myResourceGroup" -VMScaleSetName "myVMSS"
    Add-AzVmssExtension -VirtualMachineScaleSet $VMSS -Name "InfiniBandDriverWindows" -Publisher "Microsoft.HpcCompute" -Type "InfiniBandDriverWindows" -TypeHandlerVersion "1.0"
    Update-AzVmss -ResourceGroupName "myResourceGroup" -VMScaleSetName "MyVMSS" -VirtualMachineScaleSet $VMSS
    Update-AzVmssInstance -ResourceGroupName "myResourceGroup" -VMScaleSetName "myVMSS" -InstanceId "*"

    For more information, see Virtual machine extensions and features. You can also work with extensions for VMs deployed in the classic deployment model.

  • RDMA network address space - The RDMA network in Azure reserves the address space To run MPI applications on instances deployed in an Azure virtual network, make sure that the virtual network address space does not overlap the RDMA network.

Cluster configuration options

Azure provides several options to create clusters of Windows HPC VMs that can communicate using the RDMA network, including:

  • Virtual machines - Deploy the RDMA-capable HPC VMs in the same availability set (when you use the Azure Resource Manager deployment model). If you use the classic deployment model, deploy the VMs in the same cloud service.

  • Virtual machine scale sets - In a virtual machine scale set, ensure that you limit the deployment to a single placement group. For example, in a Resource Manager template, set the singlePlacementGroup property to true.

  • MPI among virtual machines - If MPI communication if required between virtual machines (VMs), ensure that the VMs are in the same availability set or the virtual machine same scale set.

  • Azure CycleCloud - Create an HPC cluster in Azure CycleCloud to run MPI jobs on Windows nodes.

  • Azure Batch - Create an Azure Batch pool to run MPI workloads on Windows Server compute nodes. For more information, see Use RDMA-capable or GPU-enabled instances in Batch pools. Also see the Batch Shipyard project, for running container-based workloads on Batch.

  • Microsoft HPC Pack - HPC Pack includes a runtime environment for MS-MPI that uses the Azure RDMA network when deployed on RDMA-capable Linux VMs. For example deployments, see Set up a Linux RDMA cluster with HPC Pack to run MPI applications.

Other sizes

Next steps