Priority tagging of vSAN traffic

 Background

According to Cisco COS is defined as "Class of Service (CoS) or Quality of Service (QoS) is a way to manage multiple traffic profiles over a network by giving certain types of traffic priority over others. "

Note that there's also a similar technology called DSCP that can used in more or less the same way.

When using a vSphere Distributed Switch it's possible to configure this and create fairly granular rules per Port Group. It's not at all limited to vSAN traffic even though that was our use case.

Task

I was asked by the networking guys if we could enable this functionality for vSAN traffic by setting COS=3.

Solution

Identify the port group associated with the vmkernel adapter used by vSAN and choose  Edit Settings. / Advanced and enable Traffic filtering and marking. 

At configure level for the port group you will need to create the rule as outlined in the following steps:

Now that it was turned on it was instantly visible to the networking guys as they started seeing traffic within UC3 (Priority Group 3).