Users Guide

142 Fabric OS Administrator’s Guide
53-1002920-02
Buffer credit management
5
Calculating the number of buffers required given the distance, speed,
and frame size
If you know the distance, speed, and frame size for a given port, you can use the portBufferCalc
command to calculate the number of buffers required. If you omit the distance, speed, or frame
size, the command uses the currently configured values for the port. Given the buffer requirement
and port speed, you can use the same distance and frame size values when using the
portCfgLongDistance command.
To determine the number of buffers required, complete the following steps:
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the portBufferCalc command and provide values for the distance, port speed, and frame
size.
The following example calculates the number of buffers required for an 8-Gbps port on a 100-km
link with an average frame size of 512 bytes.
switch:admin> portbuffercalc 9/4 -distance 100 -speed 8 -framesize 512
1606 buffers required for 100km at 8G and framesize of 512 bytes
Allocating buffer credits for F_Ports
The default configured F_Port buffer credit is fixed at eight buffers. You can use the
portCfgFPortBuffers command to configure a given port with the specified number of buffers.
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the portCfgFPortBuffers command.
switch:admin> portcfgfportbuffers --enable 2/44 12
Note that in the sample commands provided in the following procedure, 12 buffers are
configured for an F_Port.
To disable the port buffer configuration and return to the default buffer allocation, use the --disable
option.
switch:admin> portcfgfportbuffers --disable 2/44
NOTE
The configured number of buffers for a given port is stored in the configuration database and is
persistent across reboots. The F_Port buffer feature does not support EX_Port, Port Mirroring,
Long-Distance, L_Port, FastWrite, QoS, and Trunk Area enabled ports. F_Port Buffers are mutually
exclusive to E_Port Credits
Monitoring buffers in a port group
Use the portBufferShow command to monitor the remaining buffers on a long-distance link and to
monitor the average frame size and average buffer usage for a given port.
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the portBufferShow command.