Users Guide

Fabric OS Administrator’s Guide 145
53-1002920-02
Buffer credit management
5
NOTE
The distances in table 17 assume that QoS is enabled. If QoS is disabled, the maximum supported
distances are higher, because QoS requires an additional 20 buffer credits per active port.
Estimated maximum equally distributed distance = 1-port maximum distance/Number of ports
For example, for three ports running at 2 Gbps on a Brocade 300 switch, the maximum equally
distributed distance is calculated as 486 / 3 = 164 km.
Downgrade considerations
When Fabric OS firmware is downgraded from version 7.1 to an earlier version, the effect depends
on whether the number of buffer credits for the long-distance port is configured with the -framesize
and -distance options or with the -buffers option.
When a port is configured with –framesize and –distance options
In Fabric OS v7.1, if you configure the port by using the -distance option alone, the reserved buffers
are calculated according to the distance. If you configure both the -framesize option and the
-distance option, more buffers will be reserved, depending on the frame size.
With a firmware downgrade, those ports that were configured with more reserved buffers will keep
the reserved buffers as long as the ports remain online. The next time the port is toggled, buffers
will again be reserved on the basis of distance only.
6547 7714 3857 1928 1542 964
7800 410 205 102 N/A N/A
VA-40FC 1694 847 423 N/A N/A
Brocade Encryption Switch 1392 696 348 N/A N/A
FC8-16 1294 647 323 N/A N/A
FC8-32 1294 647 323 N/A N/A
FC8-32E 5190 2595 1297 1038 648
FC8-48 1230 615 307 N/A N/A
FC8-48E 4486 2243 1121 897 560
FC8-64 *** Extended Fabrics is not supported on this blade ***
FC16-32 5190 2595 1297 1038 648
FC16-48 4486 2243 1121 897 560
FS8-18 1604 802 401 N/A N/A
FX8-24 1062 531 265 N/A N/A
TABLE 16 Configurable distances for Extended Fabrics (Continued)
Maximum distances (km) that can be configured (assuming a 2112-byte frame size)
Switch/blade model 2 Gbps 4 Gbps 8 Gbps 10 Gbps 16 Gbps