TCP Segmentation Offload - Can we disable it?

[khairulnizam]

Hi,

Want to find out either we can disable TCO as I am looking at the option to move back packets processing back to server CPU as currently the CPU are under utilized. VM that we have most of the time having high IO on the network.

1. Is there any extra benefit we can gain from it?

2. Any impact?

thanks.

br,

Khairul

[mcowger]

Why would you want to disable this and add CPU overhead to your guests when you have hardware to offload it?  Having trouble understanding that decision.

It only improves performance and latency...

[khairulnizam]

Hi,

When TSO is disable at the host layer (vmnicX), can I assume that the CPU host will take the load?

Reason why I am asking this is because we have a 2k8 AD that having latency issue on the network. Windows team already perform all the troubleshootings and now they looking at the ESX host layer. I did find few comments stated by disable TSO can improve the network performance.

is this apply to the issue I am facing now?

thanks.

[mcowger]

Its very unlikely TSO is causing your issue, but you can look into enabling/disbaling it here:

http://vmetc.com/2009/03/18/using-the-enhanced-vmxnet-adapter-and-tso-in-esx-vms/

[khairulnizam]

Thanks matt. I will do the testing and update here with the result.

[DGilmour]

Can you post results?

Thx