@Legacy User
VDX is not longer supported by brocade. see below:
https://community.brocade.com/t5/Info-Feedback/Brocade-Community-Forums-Redirects-to-Extreme-Networks-Pulse/m-p/94984#M194
about you Problem:
from command Guide
Usage Guidelines
Use this command to set Performance or Density (default) operating modes for port groups 1-9 on the 27x40 GbE line card.
When a port group is configured In Performance mode, the third port in the port group is persistently disabled, but the
remaining two ports operate at up to 40 Gbps in Performance mode to achieve the 80 Gbps maximum rate for the port group.
QSFP breakout mode is only supported on ports configured in Performance mode.
If Density mode (default) is configured for a port group, all three ports in the group are enabled in Density mode, so cannot
support the 40 Gbps maximum rate. If this mode is configured on all port groups, 27 total ports are available for use.
For more information on port groups and the Performance and Density operating modes on the line card, refer to the
"Overview" chapter in the Brocade 8770-4 and 8770-8 Hardware Reference Manuals.
Enter no performance mode to restore the default value. Power off the line card before configuring operating modes.
Examples
To enable Performance mode on port group 9 of the line card in slot 3 of switch with RBridge ID 1.
switch# configure terminal
Entering configuration mode terminal
switch(config)# hardware
switch(config-hardware)# port-group 1/3/9
switch(config-port-group-1/3/9)# mode performance
%Warning: port-group mode performance is a disruptive command.
Please save the running-config to startup-config and a power-cycle for the
changes to take place.
#TheWaterCooler