Dell POWEREDGE M1000E - Manual (Page 552)

552 Fabric OS Administrator’s Guide
53-1002745-02
Extended Fabrics device limitations
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• Optimized switch buffering
When Extended Fabrics is installed on gateway switches (with E_Port connectivity from one
switch to another), the ISLs (E_Ports) are configured with a large pool of buffer credits. The
enhanced switch buffers help ensure that data transfer can occur at near-full bandwidth to use
the connection over the extended links efficiently. This efficiency ensures the highest possible
performance on ISLs.
Extended Fabrics device limitations
Note the limitations regarding the following platforms:
• 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, because of
its limited buffers. This blade does not support long-wavelength (LWL) fiber optics 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, insufficient
buffers may remain for the other ports. In this case, some of the remaining ports may come up
in degraded mode.
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 specific port. Changes made by this command are
persistent across switch reboots and power cycles.
This command supports the following long-distance link modes:
• Normal 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’s 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.
• Extended Mode (LE) — LE configures the distance for an E_Port when that distance is 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 allocation yields the
following values for 10 km:
- 10 buffer credits per port at 2 Gbps.
- 20 buffer credits per port at 4 Gbps.
- 40 buffer credits per port at 8 Gbps.
- 50 buffer credits per port at 10 Gbps
- 80 buffer credits per port at 16 Gbps