Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 138
When a port is con d with -framesize and -distance options
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Buffer-to-Buffer Credits and Credit Recovery When Fabric OS firmware is downgraded from version 7.1 to an earlier version, the effect depends on whether the number of buffer credits for the long-distance port is configured with the -framesize and -distance options or with the -buffers option. When a port is configured with -framesize and -distance options In Fabric OS v7.1, if you configure the port by using the -distance option alone, the reserved buffers are calculated according to the distance. If you configure both the -framesize option and the -distance option, more buffers will be reserved, depending on the frame size. With a firmware downgrade, those ports that were configured with more reserved buffers will keep the reserved buffers as long as the ports remain online. The next time the port is toggled, buffers will again be reserved on the basis of distance only. When a port is configured with the -buffers option A firmware downgrade from Fabric OS 7.1.0 to any earlier version is blocked when a port is configured as a long-distance port by means of the -buffers option. The following warning message is displayed: Downgrade to selected version is not allowed because few ports are configured with longdistance -buffers option. Please remove the configuration using portcfglongdistance / L0 CLI or change the configuration with -distance option on the console. NOTE The downgrade from Fabric OS 7.3.0 to 7.2.0 or 7.1.0 is not blocked due to this reason. Configuring credits for a single VC You can alter the default credit allocation for a normal distance E_Port or EX_Port so that a specific number of credits is allocated to a port. When you allocate a specific number of credits to an E_Port or EX_Port, the number of credits specified override the default credit allocation. When this feature is disabled, the default credit model is restored. Only a normal distance E_Port and EX_Port can utilize the new credit model, and the allocated credits are reserved only for that port. When this feature is enabled, the E_Port credit configuration is persistent across system reboots and High Availability (HA) failover. This feature is supported on E_Ports and EX_Ports. It does not support ports configured as F_Ports, Mirror Ports, L_Ports, and Longdistance Ports. If E_Port credits are configured on ports, you cannot move the ports from one logical switch to another. You can also allocate buffers for 2 km ICL ports. Increasing credits for normal distance E_Ports Use the following steps to allocate credits to an E_Port. 1. Connect to the switch and log in using an account assigned to the admin role. 2. Enter the portCfgEPortCredits --enable command to allocate credits to an E_Port. In the following example, 14 credits are allocated to each of the medium Virtual Channels (VCs) for non-QoS ports, and to both the medium and high VCs for QoS ports. switch:admin> portcfgeportcredits --enable 12/6 14 Success 3. Enter the portCfgEPortCredits --show command to verify that the credits have been allocated to the E_Port. In the following example, it is verified that 14 credits per VC have been allocated to the E_Port. switch:admin> portcfgeportcredits --show 12/6 E-Port Credit Configured : 14 Success. Brocade Fabric OS Administration Guide, 8.0.1 138 53-1004111-02