Network Latency on Virtual Machine

Slight network latency may cause application problem  on sensitive virtual machines. Even the network responding time is just 3 or 7 ms. There is a way to improve the  stability of responding latency – Enable RSS on NIC.

Network traffic is handled by single CPU core when RSS is disabled. Enable it will distribute the workload to 4 cores by default. You can increase CPU for RSS by change registry.

To summarize the solution. Go to Device Manager -> NIC properties -> Advance -> Find RSS option  and enable it. You will see 2 – 3 network drops when applying it.

You can refer following articles for detail.

Poor network performance or high network latency on Windows virtual machines

Virtual Receive-side Scaling in Windows Server 2012 R2

Regarding increase CPU for RSS. Read following article to learn how to modify it.

Setting the Number of RSS Processors

FC Traffic Drops After IOM Reset/Reseat/Cable Pull or UCS Upgrade

I just found a Cisco KB descripts a firmware issue may impact to ESXi FC storage performance. Please have a look whether your Cisco UCS system firmware is 2.1(2a), 2.1(2c), or 2.1(2d).

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