Optimize network throughput for Azure virtual machines

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Azure Virtual Machines (VMs) have default network settings that can be further optimized for network throughput. This article describes how to optimize network throughput for Azure Windows and Linux VMs, including major distributions such as Ubuntu.

Windows virtual machines

If your Windows virtual machine supports accelerated networking, enable that feature for optimal throughput. For more information, see Create a Windows VM with accelerated networking.

For all other Windows virtual machines, using Receive Side Scaling (RSS) can reach higher maximal throughput than a VM without RSS. RSS might be disabled by default in a Windows VM. To determine whether RSS is enabled, and enable it if it's currently disabled, complete the following steps:

  1. See if RSS is enabled for a network adapter with the Get-NetAdapterRss PowerShell command. In the following example output returned from the Get-NetAdapterRss, RSS isn't enabled.

    Name                    : Ethernet
InterfaceDescription    : Microsoft Hyper-V Network Adapter
Enabled                 : False

  2. To enable RSS, enter the following command:

    Get-NetAdapter | % {Enable-NetAdapterRss -Name $_.Name}

    This command doesn't have an output. The command changes NIC settings. It causes temporary connectivity loss for about one minute. A Reconnecting dialog appears during the connectivity loss. Connectivity is typically restored after the third attempt.

  3. Confirm that RSS is enabled in the VM by entering the Get-NetAdapterRss command again. If successful, the following example output is returned:

    Name                    : Ethernet
InterfaceDescription    : Microsoft Hyper-V Network Adapter
Enabled                 : True

Linux virtual machines

RSS is always enabled by default in an Azure Linux VM. Linux kernels released since October 2017 include new network optimizations options that enable a Linux VM to achieve higher network throughput.

Ubuntu for new deployments

The Ubuntu Azure kernel is the most optimized for network performance on Azure. To get the latest optimizations, first install the latest supported version of 18.04-LTS, as follows:

"Publisher": "Canonical",
"Offer": "UbuntuServer",
"Sku": "18.04-LTS",
"Version": "latest"

After the creation is complete, enter the following commands to get the latest updates. These steps also work for VMs currently running the Ubuntu Azure kernel.

#run as root or preface with sudo
sudo apt-get -y update
sudo apt-get -y upgrade
sudo apt-get -y dist-upgrade

If an existing Ubuntu deployment already has the Azure kernel but fails to update with errors, this optional command set might be helpful.

#optional steps might be helpful in existing deployments with the Azure kernel
#run as root or preface with sudo
sudo apt-get -f install
sudo apt-get --fix-missing install
sudo apt-get clean
sudo apt-get -y update
sudo apt-get -y upgrade
sudo apt-get -y dist-upgrade

Ubuntu Azure kernel upgrade for existing VMs

You can get significant throughput performance by upgrading to the Azure Linux kernel. To verify whether you have this kernel, check your kernel version. It should be the same or later than the example.

#Azure kernel name ends with "-azure"
uname -r

#sample output on Azure kernel:
#4.13.0-1007-azure

If your virtual machine doesn't have the Azure kernel, the version number usually begins with "4.4." If the VM doesn't have the Azure kernel, run the following commands as root:

#run as root or preface with sudo
sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get dist-upgrade -y
sudo apt-get install "linux-azure"
sudo reboot

CentOS

In order to get the latest optimizations, we recommend that you create a virtual machine with the latest supported version by specifying the following parameters:

"Publisher": "OpenLogic",
"Offer": "CentOS",
"Sku": "7.7",
"Version": "latest"

Both new and existing VMs can benefit from installing the latest Linux Integration Services (LIS). The throughput optimization is in LIS, starting from 4.2.2-2. Later versions contain further improvements. Enter the following commands to install the latest LIS:

sudo yum update
sudo reboot
sudo yum install microsoft-hyper-v

Next steps