Extended Fabrics Device Limitations; Long Distance Link Modes - HP SN3000B Administrator's Manual

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Extended Fabrics device limitations

Extended Fabrics device limitations
Note the limitations regarding the following platforms:
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Long distance link modes

Use the portCfgLongDistance command to support long distance links and to allocate sufficient
numbers of full size frame buffers on a particular port. Changes made by this command are
persistent across switch reboots and power cycles. This command supports the following
long-distance link modes:
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452
Brocade 8000 FCoE switch
Extended Fabrics is not supported on this platform.
FC8-64 port blade
Brocade recommends that you do not use the FC8-64 port blade for long distance, due to
limited buffers. This blade does not support LWL and supports limited distance. However, you
can use the portCfgLongDistance command to reserve frame buffers for the ports intended to
be used in long distance mode through DWDM.
There is a limited number of reserved buffers used for long distance for each blade. If some
ports are configured in long distance mode and have buffers reserved for them, there may be
insufficient buffers for the other ports. In this case, some of the remaining ports may come up
in degraded mode.
Static Mode (LO) - L0 is the normal (default) mode for an E_Port. It configures the E_Port as a
standard (not long distance) ISL. A total of 20 full-size frame buffers are reserved for data
traffic, regardless of the E_Port operating speed; therefore, the maximum supported link
distance is up to 5 km at 2 Gbps, up to 2 km at 4 Gbps, and up to 1 km at 8, 10, and 16 Gbps.
Static Mode (LE) - LE configures an E_Ports distance greater than 5 km and up to 10 km. LE
does not require an Extended Fabrics license. The baseline for the buffer credit calculation is
one buffer credit per km at 2 Gbps. This yields the following values for 10 km:
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10 buffer credits per port at 2 Gbps.
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20 buffer credits per port at 4 Gbps.
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40 buffer credits per port at 8 Gbps.
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50 buffer credits per port at 10 Gbps
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80 buffer credits per port at 16 Gbps
Dynamic Mode (LD) - LD calculates BB credits based on the distance measured during port
initialization. Brocade switches use a proprietary algorithm to estimate distance across an ISL.
The estimated distance is used to determine the BB credits required in LD (Dynamic) extended
link mode based on a maximum Fibre Channel payload size of 2,112. You can place an upper
limit on the calculation by providing a desired_distance value. Fabric OS confines user entries
to no larger than what it has estimated the distance to be. When the measured distance is
more than desired_distance, the desired_distance (the smaller value) is used in the
calculation.
Fabric OS Administrator's Guide
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