Windows Server 2012 : Managing virtual machines (part 2) - Optimizing network performance

You can use the main page for a virtual network adapter in the virtual machine settings dialog box to enable and configure bandwidth management for the adapter. Bandwidth management, also known as Hyper-V quality of service (Hyper-V QoS), is a new feature in Windows Server 2012 that allows you to guarantee network traffic levels for virtual network adapters and virtual switches. In the previous version of Hyper-V, you could configure only the maximum bandwidth allowed for a virtual network adapter. New in Windows Server 2012 Hyper-V is the ability to also configure a minimum bandwidth for a virtual network adapter, as shown in Figure 2.

Figure 2. Configuring maximum and minimum bandwidth for a virtual network adapter.

You can also use the Set-VMNetworkAdapter cmdlet to configure bandwidth management settings for a virtual network adapter using Windows PowerShell. The Set-VMNetworkAdapter cmdlet allows you to specify maximum and minimum bandwidth in either Mbps or in terms of a relative weight between 0 and 100. You can use the latter approach to control how much bandwidth the virtual network adapter can have compared to other virtual network adapters connected to the same virtual switch. For example, the following command can be used to implement bandwidth fair-sharing, in which every virtual network adapter for the specified virtual machines is assigned the same minimum bandwidth weight:

PS C:\> Get-VMNetworkAdapter -VMName SRV-A,SRV-B,SRV-C | Set-VMNetworkAdapter
-MinimumBandwidthWeight 1

You can also configure a minimum bandwidth (either absolute or relative) for a virtual switch by using the Set-VMSwitch cmdlet. You can also do this when you create a new virtual switch using the New-VMSwitch cmdlet. You cannot configure this setting using Hyper-V Manager.

Other network performance optimizations, such as SR-IOV and VMQ, are also available in Windows Server 2012 Hyper-V but require specialized hardware. These additional optimizations can be configured either on the Hardware Acceleration subpage for a network adapter in the virtual machine settings dialog box or by using Windows PowerShell cmdlets.