Hi, I understand that for an 8-port 10Gb module (6509) ports 1,2,5 & 6 are the only performance 10 Gb ports (true 20Gb at full duplex) Does this mean I will not get the 10Gb throughput for another port, I'm debating whether or not it is worth moving my 10Gb optical circuit (dark fiber) on a port #4 to a "performance" port such as 1,2,5 or 6. Thanks to all for your input.
The 6708-10G card has 2 connections to the switch fabric
Fabric Channel #1: Ports 2, 3, 6, 8
Fabric Channel #2: Ports 1, 4, 5, 7
As far as i understand it that means that if you want 10Gbps on the port you can only use 2 ports from each fabric channel.
Cisco have provided a command to automatically shutdown ports 3,4,7,8 so that you are not oversubscribed on this module. But i don't think you have to use 1,2,5 & 6. You could use port 4 as long as you only used one other port from that fabric channel group ie. 1,5 or 7 and you would still get the full 10Gbps throughput.
Note i haven't actually tested the above but it is based on the way that all the 6500 fabric enabled modules work.