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Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

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Configuring the PFC Buffer in a Switch Stack

In a switch stack, you must configure all stacked ports with the same PFC configuration. In addition, you must configure a separate buffer of memory allocated exclusively to a service pool accessed by queues on which priority-based control flows are mapped.

These PFC-enabled queues ensure the lossless transmission of storage and server traffic. The buffer required for the PFC service pool is calculated based on the number of ports and port queues used by PFC traffic.

You can configure the size of the PFC buffer for all switches in a stack or all port pipes on a specified stack unit by entering the following commands on the master switch.

  • Configure the PFC buffer for all switches in the stack. CONFIGURATION mode [no] dcb stack-unit all pfc-buffering pfc-port {1-56} pfc-queues {1-2} By default, the PFC buffer is enabled on all ports on the stack unit.
  • Configure the PFC buffer for all port pipes in a specified stack unit by specifying the port-pipe number, number of PFC-enabled ports, and number of configured lossless queues. CONFIGURATION mode [no] dcb stack-unit stack-unit-id [port-set port-set-id] pfc-buffering pfc-ports {1-56} pfc-queues {1-2} Valid stack-unit IDs are 0 to 5. The only valid port-set ID (port-pipe number) is 0.
Dell Networking OS Behavior:

To achieve lossless PFC operation, the PFC port count and queue number used for the reserved buffer size that is created must be greater than or equal to the buffer size required for PFC-enabled ports and lossless queues on the switch.

For the PFC buffer configuration to take effect, you must reload the stack or a specified stack unit (use the reload command at EXEC Privilege level).

If you configure the PFC buffer on all stack units, delete the startup configuration on both the master and standby, and reload the stack, the new master (previously standby) generates the following syslog message for each stack unit when it boots up: PFC_BUFFER_CONFIG_CHANGED is generated for all stack units .

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