Qlogic SANbox2 SANbox2-64, Руководство пользователя

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6 – Managing Ports
Configuring Ports
6-12 59048-01 A
6.2.5
Changing Buffer-to-Buffer Credits
Each port has a receive buffer capacity of 12 Fibre Channel frames or credits
which is equal to approximately 24K bytes. Port buffer credits can be changed on
ports to allow connections to non-QLogic switches that have different port buffer
capacities. To change port buffer credits, do the following:
1. Select one or more ports in the faceplate display.
2. Open the Port menu and select Port Properties.
3. In the E_Port BB Credits field, enter the new number in the range from
0–255.
4. Choose the OK button to write the new buffer-to-buffer setting to the switch.
6.2.6
I/O Stream Guard
The I/O Stream Guard feature suppresses Registered State Control Notification
(RSCN) messages on a port basis.
6.2.7
Extending Port Credits
Each port is supported by a data buffer with a 12 credit capacity; that is, 12
maximum sized frames. For fibre optic cables, this enables full bandwidth service
over a distance of 20 kilometers at 1 Gbps (0.6 credits/Km), or 10 kilometers at 2
Gbps (1.2 credits/Km). Longer distances can be spanned at full bandwidth by
borrowing credits from designated donor ports thus pooling the buffer capacities.
This is called credit extension. Each donor port contributes 11 credits to the pool
from which the recipient ports can draw. For example, one donor port contributes
11 credits to the pool from which a recipient draws for a total of 23 credits (11+12).
This provides approximately 38 Km at 1 Gbps (23÷0.6) or 19 Km at 2 Gbps
(23÷1.2).
To extend port buffer credits, do the following:
1. In the faceplate display, select the ports that are to serve as donor ports.
Open the Port menu and select Port Properties. In the Port Properties
window, choose the Donor radio button and choose OK.
Note: Donor ports cannot transmit or receive data.