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Child Partition With and Without VSP/VSC Design Page 2

When you install Integration Services Components in a virtual machine, the following drivers are installed to improve the virtual machine communication with the Parent Partition:

  • For Display Adapter - C:\Windows\System32\VMBusVideoD.dll and C:\Windows\System32\Drivers\VMBusVideoM.Sys
  • For Human Interface Devices - C:\Windows\System32\Drivers\hidusb.sys and C:\Windows\System32\Drivers\VMBusHID.SYS
  • For Network Adapters - C:\Windows\System32\Drivers\NetVSC60.sys
  • For Storage Controllers - C:\Windows\System32\Drivers\StorVSC.sys

Apart from the drivers mentioned above, a VMBUS device is also added. It uses the VMBUS.sys driver Server Tutorials located in the "C:\Windows\System32\Drivers" folder.

The VSC drivers talk to the VMBUS.sys driver loaded in the virtual machine. VMBUS.sys communicates with the VMBUS.sys running in the Hyper-V Parent Partition which, in turn, communicates with the corresponding VSP running in the Parent Partition to enable direct communication, avoiding communication with the device emulation layer.

To confirm if a virtual machine is successfully communicating with the Parent Partition using the VSP/VSC design, you can take a look at the Device Manager in the virtual machine as shown in the below screenshot:

Hyper-V VM Device Manager - Figure 2

If the corresponding VSC is functioning properly on the virtual machine you will see "Microsoft Hyper-V Video" for Video VSC, "Microsoft Hyper-V Virtual Keyboard" for HID VSC, "Microsoft Hyper-V Network Adapter" for Network VSC and "Microsoft Hyper-V SCSI Controller" for Storage VSC, which is shown in the image above.

If these drivers are corrupted or are not present in the virtual machine, the virtual machine communication will always take place using device emulation.

In Generation 2 virtual machines, announced with Windows Server 2012 R2 at TechED North America, the VMBUS and VSP/VSC design is always available. You cannot turn it off — and there's no reason to turn it off as it improves the virtual machine communication. You can read more about Generation 2 virtual machines in last month's article on Generation 1 and Generation 2 VMs.

Child Partition Without VSP/VSC Design

The 2nd child partition hosted in the above image doesn't implement VSC functionality. It could be a case of either the Integration Service components not having been installed or the operating system is not supported by Hyper-V. The 2nd child partition always relies on device emulation. It always communicates to the parent partition using emulated device drivers, which will reduce the overall performance of virtual machine.


In this article we learned how the VSP and VSC components of Hyper-V play an important role in improving the communication between virtual machines and the parent partition. We also saw that these components are available as part of the Integration Services that are installed in a virtual machine. Without VSP/VSC components, a virtual machine operating system will use the operating system-provided drivers for communication, which will result in degraded performance for the virtual machine.

Nirmal Sharma is a MCSEx3, MCITP and Microsoft MVP in Directory Services. He has specialized in Microsoft Technologies since 1994 and has followed the progression of Microsoft Operating System and software. In his spare time, he likes to help others and share some of his knowledge by writing tips and articles on various sites and contributing to Solution IDs for www.Dynamic-SpotAction.com. Nirmal can be reached at nirmal_sharma@mvps.org.

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This article was originally published on October 9, 2013
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