Hi All,
I have an issue with our Windows Server 2012 Hyper-V hosts that I can't seem to figure out. Situation:
2 x Dell PowerEdge R815 servers with AMD opteron 6376 16 core CPU's and 128 GB RAM running Windows Server 2012 with Hyper-V.
2 virtual machines running on the same physical host and connected to the same virtual switch show high TCP connection latencies. One virtual machines runs a SQL Server 2012 database instance and a Dynamics AX 2012 R2 instance. The other machine a SharePoint 2013 instance and the AX client. We see latencies of 20ms and higher on most of the TCP connections that are made from the sharepoint machine to the sql server machine.
At first I thought it might have something to do with the physical NIC's. It turned out that VMQ wasn't correctly supported by the firmware of the Broadcom BCM5709c cards. By default this setting is enabled. Turning off the VMQ setting somewhat improved the situation but the latencies are still at 8ms and higher.
What I don't understand is what influence enabling/disabling VMQ should have on network performance. As I understand it now virtual machines connected to the same virtual switch bypass the physical altogether. Another point is that VMQ should actually improve performance, not decrease it.
Another question I have is about the various tcp offloading settings on the physical NIC's. After installing the new firmware and drivers from Dell most of these settings are set to disabled. The documents I have been able to find talk about Windows Server 2008, any thought how these settings relate to Windows Server 2012 and whether they should be enabled?
Thanks in advance for your time and thoughts
Kind regards,
Dennes Schuitema