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Planning
Performance
The switch supports class 2 and class 3 Fibre Channel service at transmission rates of 2 Gbps,
with a maximum frame size of 2148 bytes.
Related performance characteristics include:
Distance
Consider the physical distribution of devices and switches in the fabric. See "Specifications"
on page 59 for more information about cable types and transceivers.
Each Fibre Channel port is supported by a data buffer with a 16 credit capacity; that is, 16
maximum sized frames. For fiber optic cables, this enables full bandwidth over a distance of
13 kilometers at 2 Gbps (1.2 credits/Km). Beyond this distance, however, there is some loss of
efficiency because the transmitting port must wait for an acknowledgement before sending the
next frame.
Longer distances can be spanned at full bandwidth by extending credits to the ports. Each port
can donate 15 credits to a pool from which a recipient port can borrow. The recipient port also
loses a credit in the process. For example, you can configure a recipient port to borrow 15
credits from one donor port for a total of 30 credits (15+15=30). This supports communication
over approximately 25 Km at 2 Gbps (30÷1.2).
Bandwidth
Bandwidth is a measure of the volume of data that can be transmitted at a given transmission
rate. The Fibre Channel ports transmit and receive at a rate of 2 Gbps, for a maximum
bandwidth of 200 MB.
Latency
Latency is a measure of how fast a frame travels from one port to another. Factors that affect
latency include transmission rate and the source/destination port relationship. 2 Gbps to
2 Gbps transmissions have a latency factor < 0.4
24
Distance
Bandwidth
Latency
µsec.
HP StorageWorks 2/8q Fibre Channel Switch Installation Guide
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