iSCSI connection problem; Control QOS Group v. QOS GRoup

[jgsmith]

On the two Nexus 3172T's used for iSCSI traffic, we see dropped unicast packets in the "Control QOS Group" statistics on every interface. In the "QOS Group" statistics, we see dropped multicast packets.

Is there any documentation that might identify what the Control QOS Group is (or can anyone tell me) ?

From what little I've found, it sounds like the packets in this group carry traffic controls. If thats true, how would you diagnose and resolve the dropped packet problem ?

Counters are cleared daily; the packet drops are consistent.

Thanks for any ideas.

[Reza Sharifi]

The issue may be related to the low amount of shared buffer (12mb) on these switches.  I have seen the same issue with FEXs and storage and the only solution was to replace them with a switch with a higher amount of buffer. I would open a ticket with TAC as this may be a known issue to them.

Here is a link on the architecture of the switch

https://people.ucsc.edu/~warner/Bufs/cisco-3100-arch.pdf

HTH