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Understanding "Preferred" speed on VC FCoE server profile

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Understanding "Preferred" speed on VC FCoE server profile

John had a Virtual Connect bandwidth setting question:






I’ve got a blade enclosure running VC 4.10, and has two FlexFab modules. Gen8 bl460c blades. The uplinks show that 3 of the four are at 8gb, while one is at 4gb: ( not sure when this happened, but originally all were at 8gb)




The servers that use X1 above have their FCOE server profile speed set to “Preferred”.




Manual says:


Preferred—The speed of the network is the same as the preferred speed of the

network to which the connection is associated. If no preferred speed is

configured for a network, it behaves like "Auto".


So, in this instance, what speed would the blades corresponding FCoE FlexFab port be operating at ?

Does this mismatch generally cause issues ( ok, I realize this is a very non-specific question)….






Reply from David:




The SAN Fabrics are showing Uplink speeds, external SAN switch.


The FCoE HBA… is showing Downlink speeds to the server NIC/HBA.


The two are independent of each other. Downlink FCoE speeds default to 4Gb to leave 6Gb for the Ethernet NICs.

These can be changed as needed.


The Uplink speeds will depend on the VC setting and the external connected switch.

If set to ‘Auto’ for speed, then it will sink to the external switch set speed.

It can also be set to 4Gb, 8Gb to lock in a specific speed.


I would edit the top FCOE_A line to verify that it shows ‘Auto’ under the Speed column.

I would leave it at ‘Auto’ and have the SAN team check the SAN switch port speed.

Also verify that the SFP is rated at 8Gb. Have not seen a 4Gb SFP for a long time.