What if you face very slow network performance for an Hyper-V virtual machine?
Posted by Jacques on Tuesday, 25 March 2008
Recently, I installed the Hyper-V role (still a beta version) on a new Dell PowerEdge 2950 with Windows 2008 x64 Enterprise.
The server was equiped with two dual port gigabit NIC interfaces, one Broadcom Nextreme II on board and one Intel PRO 1000PT Dual PortI on the PCIe x4 bus .
Virtual machine using a virtual network created on an Intel NIC port showed extremely poor network performance. When accessing the virtual machine using the console of the Hyper-V manager on the parent partition, the performance was excellent. But remote desktop was extremely slow.
I remembered that Windows 2008 was installed on this server with the TOE (TCP Offload Engine) physical license key pluged in on the mother boad.
In this scenario, as I could read in the Technet Windows Virtualization forum, it is advisable to disable TCP Offloading in the VM (you just let it on the host).
So I created and set a new registry value in each VM connected to a virtual network using an Intel NIC port:
Key: HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
Value(DWORD): DisableTaskOffload = 1
After disabling TCP offload on the VM, the network performance was just perfect.
December 18th, 2008 at 3:24
Funny we have RTM Hyper-V and the host 2008 NIC screams, we get over 500Mbps, but the guest which is 2003 SP2 with integration services gets only 58Mbps, a factor of 10x difference degradation for the guest, it is the only active guest!
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May 31st, 2010 at 7:58
Thank you! This worked fine on 2008R2, Remote Desktop to guests was unusable, and now works fine.
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