HP StorageWorks SN6000 Fibre Channel Switch Installation and Reference Guide 21
Extending credits requires a minimum cable length that is dependent on transmission speed, but is
independent of the number of credits borrowed. Extending credits using short cables can cause excessive
port resets. Table 5 describes the minimum cable lengths for a port with extended credits.
For more information about cable types, transceivers, and maximum supported distances, see the SAN
Design Reference Guide available at the HP website: http://www.hp.com/go/SANdesignguide
.
Bandwidth
Bandwidth is a measure of the volume of data that can be transmitted at a given transmission rate. An SFP
port can transmit or receive at nominal rates of 1, 2, 4, or 8 Gb/s depending on the device to which it is
connected. This corresponds to full duplex bandwidth values of 212 MB, 424 MB, 850 MB, and 1700 MB
respectively. XPAK ports transmit at a nominal rate of 10 Gb/s which corresponds to a full duplex
bandwidth value of 2550 MB. With an SN6000 Stackable 20Gb ISL Upgrade LTU, XPAK ports can
transmit at a nominal rate of 20 Gb/s (5100 MB bandwidth).
Multiple source ports can transmit to the same destination port if the destination bandwidth is greater than
or equal to the combined source bandwidth. For example, two 2 Gb/s source ports can transmit to one 4
Gb/s destination port. Similarly, one source port can feed multiple destination ports if the combined
destination bandwidth is greater than or equal to the source bandwidth.
In multiple chassis fabrics, each link between chassis contributes 424, 850, 1700, 2550 or 5100
megabytes of bandwidth between those chassis, depending on the speed of the link. When additional
bandwidth is needed between devices, increase the number of links between the connecting switches. The
switch guarantees in-order delivery with any number of links between chassis.
Table 5 Extended credit minimum cable lengths
Transmission Speed Minimum Cable Length
1 Gb/s 3 kilometers
2 Gb/s 1.5 kilometers
4 Gb/s 0.75 kilometers
8 Gb/s 0.37 kilometers
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