3 – Planning
Performance
59225-00 B 3-5
A
3.3.2
Bandwidth
Bandwidth is a measure of the volume of data that can be transmitted at a given
transmission rate. A Fibre Channel port can transmit or receive at nominal rates of
1-Gbps, 2-Gbps, or 4-Gbps depending on the device to which it is connected. This
corresponds to actual bandwidth values of 103 MB, 206 MB, and 412 MB
respectively. 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 1-Gbps source ports can transmit to one 2-Gbps 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 103, 206, or 412
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.
3.3.3
Latency
Latency is a measure of how fast a frame travels from one port to another. The
factors that affect latency include transmission rate and the source/destination
port relationship as shown in Table 3-2.
Table 3-2. Port-to-Port Latency
Destination Rate
Source Rate
Gbps 1 2 4
1
< 0.6 µsec
< 0.8 µsec
1
1
Based on minimum frame size of 36 bytes. Latency increases for larger frame sizes.
< 0.8 µsec
1
2
< 0.5 µsec < 0.4 µsec
< 0.4 µsec
1
4
< 0.4 µsec < 0.3 µsec < 0.2 µsec
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