Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 274
Configuring the PFC Buffer in a Switch Stack, Dell Networking OS Behavior, pfc mode
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The range is from 0 to 3. Separate the queue values with a comma; specify a priority range with a dash; for example, pfc no-drop queues 1,3 or pfc no-drop queues 2-3. The default: No lossless queues are configured. NOTE: Dell Networking OS Behavior: By default, no lossless queues are configured on a port. A limit of two lossless queues is supported on a port. If the amount of priority traffic that you configure to be paused exceeds the two lossless queues, an error message displays. Reconfigure the input policy using a smaller number of PFC priorities. If you configure lossless queues on an interface that already has a DCB input policy with PFC enabled (pfc mode on), an error message displays. 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 {1-64} 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 pfcports {1-64} 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: If you configure PFC on a 40GbE port, count the 40GbE port as four PFCenabled ports in the pfc-port number you enter in the command syntax. 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). 274 Data Center Bridging (DCB)
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