Broadcom and Hyper-V VMQs

There have been a lot of posts on the internet discussing VMQ’s. Microsoft had published this LINK to ensure that the best performance was experienced on Virtual machines. VMQ is supposed to offer an intelligent buffer, whereby virtual machines benefit from network cards which can offload and prioritise virtual machine traffic. The fact is that the Broadcom cards cause high latency issues, and inconsistency with network traffic.

I tried a few tests:

1.5 GB file:

• Copying from Physical Machine to Physical Machine:  <10 seconds
• Copying from Virtual machine to Physical Machine: 34 Seconds
• Copying from Virtual to Virtual machine: >1 minute

This pointed me to the settings within Hyper-V for the Networking interface and the iSCSI disk layer. I first checked the disks, and the IOPS on the SAN was hitting a maximum of 600 IOPS which is less than average throughput for the SAN, considering there are 24 virtual machines on the SAN volume. Then I tried the network throughput by using a few linux tools, and this proved that the Network interface was at fault. The strangest thing was that the throughput would hit about 200MB/sec and then drop off to about 15K/sec and then spike back up again. I then looked at the network interface and disabled the following setting within the network adapter:

Once this was completed then performance of the virtual machines suddenly increased. They are now running as fast as the Physical ones. However more performance gains were found when moving to Intel cards and the network traffic was very stable.

So I took the time to upgrade the servers to Intel cards and now everything works pefectly