Q-Logic 16HA user manual Distance, Port Buffer Credits

Cable Fibre Channel Devices to the Switch

Distance

The maximum distance between each adapter and the Switch depends on the type of GBICs and the type of cable installed. Refer to Appendix A Reference Informa- tion for this information. Also, the speed and Fibre Channel Revision Level of each adapter must be compatible with the Switch and the type of I/O media of each adapter must be compatible with the particular GBIC on the Switch.

Port Buffer Credits

Each port has eight buffer credits. This allows a cable length up to 13 km at 1 Gbps without performance degradation. Buffer credits can be extended for F_Ports and T_Ports to maintain performance over longer cable lengths. Credits are extended by chaining ports together. You can chain 1, 2, or 3 donor ports to the recipient F_Port or T_Port adding 8 credits for each chained port. For example, chaining one donor ports yields 16 credits, two donor ports yields 24 credits, and three donor ports yields 32 credits.

To extend buffer credits, the switch must be cabled and configured properly. The recipient F_Port or T_Port must be configured for extended credits using switch management. The following rules apply when chaining ports:

•Credits can be extended only for F_Ports and T_Ports. The recipient F_Port or T_Port must occupy the lowest numbered port in an ASIC group. For example, port 1 or port 5 can be credit recipients, but not port 2. Refer to “Tuning” on page 2-9for information about ASIC groups.

•Define recipient ports by port mode using switch management. Port modes for recipient F_Ports are: F_Ext16, F_Ext24, or F_Ext32. For example, to extend credits for port 1 to 32 credits as an F_Port, define the port mode as F_Ext32. Ports 2, 3, and 4 automatically become credit donors ports, and any external connections to the donor ports are disabled. To chain T_Ports, define recipient and donor ports as you would for an F_Port. When you cable the T_Port, it will self-configure with extended credits.

•The recipient port and all donor ports must be members of the same ASIC group. For example, you can chain ports 1 through 4, and 5 through 8, but not 3 through 6. Refer to “Tuning” on page 2-9for information about ASIC groups.

•Chained ports must be sequential. For example, if port 5 is the recipient port, you can chain ports 5 and 6, but not 5 and 7.

2-10Installation		SANbox-16HA Fibre Channel Switch
	59005-03 Rev. A	Installer’s/User’s Manual