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Fibre Channel (SAN)

Occasional Contributor
Posts: 8
Registered: ‎05-06-2009
Accepted Solution


Recently I upgraded my switches (8510-8) to FOS version 7.4.1d and also enabled Slow Drain Device Quarantine (SDDQ).
Before enabling the SDDQ feature, I did read the "Monitoring and Alerting Policy Suite Administrators Guide 7.4.1".

Reading the SDDQ, the documentation says, that it "allows MAPS to identify a slow-draining device and quarantine it by automatically moving all traffic destined to the F_Port that is connected to the slow-draining device to a low-priority VC so that the traffic in the original VC does not experience backpressure."

What is "a low-priority VC"?

Is that internally in the switch (backend) or ISL´s channels?
I´m using Virtual Fabric on all my switches.





Broadcom Moderator
Posts: 415
Registered: ‎08-31-2009




SDDQ is running with QoS enable (Quality of Service).

There are different VCs (Virtual Channels) for high, low and medium priority traffic.

Without congestion, only medium Virtual Channels are used. If a switch detect a slow drain device, it will move the data flow to that device to a low priority VC and will advise all others switches to move the flow for that device to the low priority VC. 

Any and all information provided by me is not reviewed, approved or endorsed by Brocade and is provided solely as a convenience for Brocade customers. All systems and all networks are different and unique. If you have a service affecting network problem, please open a TAC service request for service through Brocade, or through your OEM equipment provider. If this provided you with a solution to this issue, please mark it with the button at the bottom "Accept as solution"

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