HP STORAGEWORKS A7540-96010 User Manual download pdf (Page 24)

Planning

24 HP StorageWorks 2/8q Fibre Channel Switch Installation Guide

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

■ Bandwidth

■ Latency

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

µsec.

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HP STORAGEWORKS A7540-96010 User Manual Page 24