LARGE PACKET LOSS USING VMXNET3

vQuicky – 

> Large packet loss occurring in guest OS due to traffic bursts.

> Fix is to increase the receive and transmit buffer space within the guest operating system itself.

> Issue has been seen in ESXi 4.x and ESXi 5.x

inDepth – 

I haven’t experienced any but VMware KB came out with an article where while using ESXi 4.x and 5.x versions you see significant packet loss during burst traffic to your vms when they are configured with VMXNET3 vnics. The issue occurs during high traffic bursts only.

For example you have a 8-5 server or a file dump server which experiences large bursts of traffic at some set time. Users all logging in at 8 AM will cause high traffic burst possibly. VMware has confirmed that there is heavy packet loss due to lack of receive and transmit buffer space.

The fix of the issue is to increase the number of buffers in the guest operating system itself. VMware’s KB article lists the below as the steps to do so.

1. Click Start > Control Panel > Device Manager.
2. Right-click vmxnet3 and click Properties.
3. Click the Advanced tab.
4. Click Small Rx Buffers and increase the value. The default value is 512  and the maximum is 8192.
5. Click Rx Ring #1 Size and increase the value. The default value is 1024 and the maximum is 4096.

You have more info at the KB article here.

Hope this helps if you had customer’s calling in complaining of low performance 🙂