HP Fabric OS v7.0.1, Administrator'S Manual

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460 Fabric OS Administrator’s Guide
53-1002446-01
Buffer credit management
23
4. Use the following formula to calculate the number of buffer-to-buffer credits to allocate:
BB credits = roundup [desired_distance * (data_rate / 2.125)]
Using the values for desired_distance and data_rate from step 1 and step 3 , the value for BB
credits is calculated as follows:
BB credits = roundup [(207 * 8.5) / 2.125] = 828
NOTE
This formula does not work with LD mode because LD mode checks the distance and limits the
estimated distance to the real value of 100 km. LS mode allows for the necessary
desired_distance
based on the data size entered, regardless of the distance.
If buffer credit recovery is enabled, Fabric OS supports a BB_SC_N range of 1 to 15; therefore, it is
impossible for the
desired_distance to be more than the number of BB credits available in the pool
as determined by the calculations above. The BB credit recovery supported distance is well within
the range of all possible connections. An estimated distance of 32,768 is considerably higher than
the available BB credits and only lower values of
desired_distance are permitted by Fabric OS.
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.
Note
that in the sample commands provided in the following procedure, 12 buffers are configured
for an F_Port.
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
To disable the port buffer configuration and return to the default buffer allocation:
switch:admin> portcfgfportbuffers --disable 2/44
NOTE
The configured number of buffers for the 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, Fast Write, QoS, and Trunk Area enabled ports.
Displaying the remaining buffers in a port group
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the portBufferShow command.
switch:admin>
portbuffershow 17
User Port Lx Max/Resv Buffer Needed Link Remaining
Port Type Mode Buffers Usage Buffers Distance Buffers
---- ---- ---- ------- ------ ------- ---------- ---------
16 - - 0 - -
17 E L1 - 54 54 50km
18 - - 0 - -
19 - - 0 - - 54