Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 139
Buffer credit recovery, Buffer credit recovery over an E_Port
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Buffer-to-Buffer Credits and Credit Recovery Buffer credit recovery Buffer credit recovery allows links to recover after buffer credits are lost when the buffer credit recovery logic is enabled. The buffer credit recovery feature also maintains performance. If a credit is lost, a recovery attempt is initiated. During link reset, the frame and credit loss counters are reset without performance degradation. Credit recovery is supported on E_Ports, F_Ports, and EX_Ports. Buffer credit recovery is enabled automatically across any longdistance connection for which the E_Port, F_Port, or EX_Port buffer credit recovery mechanism is supported. For 16-Gbps and 32-Gbps FC devices and blades (Brocade 6505, 6510, 6520, G620, M6505, 6547, CR32-4, CR32-8, CR16-4, CR16-8, FC32-48, FC16-32, FC16-48, FC16-64): ∙ You can use the portCfgCreditRecovery command to disable or enable buffer credit recovery on a port. NOTE The credit recovery mode is supported when a link is in ISL_RDY mode and VC Init is off (only on VC0). Ff VC init is off, and ISL RDY mode is set, then VC0 will support credit recovery. Buffer credit recovery over an E_Port To support buffer credit recovery, E_Ports must be connected between devices that support 32 or 16 Gbps, or between devices that support 8 Gbps. ∙ Devices that support 32 Gbps - Brocade G620 - FC32-48, SX6 If a device that supports 32 Gbps is connected to a device that supports only 16 Gbps, buffer credit recovery is disabled, even if both devices are running 16 Gbps. ∙ Devices that support 16 Gbps: - Brocade 6505, 6510, 6520, M6505, 6543, 6547 - FC16-32, FC16-48, FC16-64 If a device that supports 16 Gbps is connected to a device that supports only 8 Gbps, buffer credit recovery is disabled, even if both devices are running 8 Gbps. There is a limited amount of credit recovery that occurs between 32/16G platforms and 8G platforms. The buffer credit recovery feature for E_Ports is enabled for the following flow-control modes: ∙ Normal (R_RDY) ∙ Virtual Channel (VC_RDY) ∙ Extended VC (EXT_VC_RDY) Buffer credit recovery over an F_Port Buffer credit recovery for F_Ports is supported for F_Port-to-N_Port links between a Brocade switch and Access Gateway, between a Brocade switch and an adapter, and between an Access Gateway and an adapter. For an F_Port on a Brocade switch connected to an Access Gateway, the following conditions must be met: ∙ Both devices must run Fabric OS v7.1 or later. ∙ Fabric OS must support buffer credit recovery at either end of the link. ∙ If both devices support 16 Gbps, the flow-control mode can be either Normal mode (R_RDY) or VC mode (VC_RDY); otherwise the flow-control mode must be R_RDY. Brocade Fabric OS Administration Guide, 8.0.1 53-1004111-02 139
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