A weird behavior was noticed on few Hyper-V host machines, these machines are mainly Dell Rack servers as the powerful R720 Model. These servers came with mix of Network adapters (based on your configuration) as the Broadcom built in adapters and extra Intel cards. The behavior noticed was that Virtual machines that are connected to the Broadcom NICs has poor performance and user login takes several minutes on these specific machines. VMs connected to the Intel Network card login normally and has better performance.
When I moved the VMs connected to the Broadcom NICs to the Intel NICs they behaved normally and users can login much faster. I then tried to move the VMs on the Intel Cards to Broadcom and we got the poor performance. We concluded it must be something related to the Broadcom Network card.
- Updating the Broadcom NICs to the latest driver. Still No change.
- We compared the options/Properties of Intel Card vs. Broadcom card and it was noticed that Transmit buffers in Broadcom was 200 vs 500 in the Intel cards, I tried changing it to match the Intel settings. Still No change.
- High Ping Latency in Hyper-V Virtual Machines: http://www.flexecom.com/high-ping-latency-in-hyper-v-virtual-machines/
- Slow Network Access Within Virtual Machines – Broadcom and Hyper-V: http://fundamentallygeek.blogspot.com/2012/11/slow-network-access-within-virtual.html
- VMQ feature http://technet.microsoft.com/en-us/library/gg162704(v=ws.10).aspx
VMs connected to the Intel Network card login normally and has better performance.
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