HP StorageWorks 8/20q and SN6000 Fibre Channel Switch Enterprise Fabric Management Suite User Guide 139
4. For each port, check (enable) or uncheck (disable) the checkbox in the Device Scan column. To apply
the same value for all selected ports, check the Device Scan checkbox at the bottom of the dialog box.
5. Click OK.
Auto Performance Tuning and AL Fairness
The Auto Performance Tuning feature enables the switch to dynamically control the MFS_Enable, VI_Enable
and LCF_Enable features based on the operational state of the port. The AL Fairness option controls how
frequently the switch can arbitrate for access and applies only to FL_Ports.
The Auto Perf Tuning and AL Fairness settings are configured using the Advanced Port Properties dialog
box.
To configure auto performance tuning and AL Fairness:
1. Select a switch in the fabric tree.
2. Select one or more ports in the faceplate display.
3. Select Port > Advanced Port Properties to open the Advanced Port Properties dialog box (Figure 81).
4. For each port, check (enable) or uncheck (disable) the checkbox in the Auto Perf Tuning and ALFairness
columns. To apply the same value for all selected ports, check the Auto Perf Tuning or ALFairness
checkboxes at the bottom of the dialog box.
5. Click OK.
Figure 81 Advanced Port Properties dialog box
Using the Extended Credits wizard
The Extended Credit wizard is a series of dialog boxes that leads you through the process of extending
credits based on transmission distance requirements. Warning dialog boxes are provided to help you
avoid un-intentional changes. Each port is supported by a data buffer with a 16-credit capacity; that is, 16
maximum sized frames.
For fibre optic cables, a port can transmit and receive at full bandwidth over the following approximate
distances:
• 26 kilometers at 1 Gb/s (0.6 credits/km)
• 13 kilometers at 2 Gb/s (1.2 credits/km)
• 6 kilometers at 4 Gb/s (2.4 credits/km)
• 3 kilometers at 8 Gb/s (4.8 credits/km)
Beyond these distances, some loss of efficiency occurs because the transmitting port must wait for an
acknowledgment before sending the next frame.
Longer distances can be spanned at full bandwidth on ports by extending credits to G_Ports, F_Ports, and
E_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
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