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.
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.