FCoE Cookbook for HP Virtual Connect Version 4.20 Firmware Enhancements May 2014

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Issues with FCoE performance
If FCoE throughput on servers is very low, this can be due to pause frames. It is necessary to check if the switch is
sending pause frames or if it is getting paused.
Possible Cause
 If the egress FC port is congested, then the switch will send PFC frames to the Virtual Connect uplink port. The PFC
frames are sent to reduce its FCoE rate and avoid a drop.
 If the server is slow or congested, then the server will send PFC frames to the Virtual Connect downlink port. As a
result Virtual Connect will eventually send PFC Frames to the Nexus interface.
To verify this situation, it is necessary to check the Nexus interface that is connected to the Virtual Connect modules.
When slow FCoE performance is not due to Pause Frames
 For a few iterations using the "show interface ethx/x priority-flow-control" command, the PFC frame count (RX/TX)
is not incrementing:
 For a few iterations using the "show queuing interface ethx/x" command, the pause status are detected for both RX
and TX as Inactive:
Solution:
The slow FCoE performance does not seem to be due to network congestion. Check the Nexus interface to find
information about possible link issues: