HP StorageWorks Fabric OS 6.1.1 administrator guide (5697-0235, December 2009)

Fabric OS 6.1.x administrator guide 369
• A trunking group has the same link cost as the master ISL of the group, regardless of the number of
ISLs in the group. This allows slave ISLs to be added or removed without causing data to be
rerouted, because the link cost remains constant.
• The addition of a path that is shorter than existing paths causes traffic to be rerouted through that
path.
• The addition of a path that is longer than existing paths may not be useful because the traffic will
choose the shorter paths first.
• Plan for future bandwidth addition to accommodate increased traffic.
For trunking groups over which traffic is likely to increase as business requirements grow, consider
leaving one or two ports in the group available for future nondisruptive addition of bandwidth.
• Consider creating redundant trunking groups where additional ports are available or paths are
particularly critical.
This helps to protect against oversubscription of trunking groups, multiple ISL failures in the same group,
and the rare occurrence of an ASIC failure.
• To provide the highest level of reliability, deploy trunking groups in redundant fabrics to further ensure
ISL failures do not disrupt business operations.
Initializing trunking on ports
After unlocking the ISL Trunking license, you must reinitialize the ports being used for ISLs so that they
recognize that trunking is enabled. This procedure must be performed only once.
To reinitialize the ports, you can either disable and then re-enable the switch, or disable and then
re-enable the affected ports.
To disable and re-enable the switch:
1. Connect to the switch and log in as admin.
2. Issue the switchDisable command.
3. Issue the switchEnable command.
To disable and re-enable ports:
1. Connect to the switch and log in as admin.
2. Issue the portDisable command:
portDisable [slot/]port
On Directors, slot is the slot number and port is the port number of the port you want to disable.
3. Issue the portEnable command:
portEnable [slot/]port
On Directors, slot is the slot number and port is the port number of the port you want to enable.
Performance monitoring
To implement ISL Trunking effectively, you must monitor fabric traffic to identify congested paths or to
identify frequently dropped links. While monitoring changes in traffic patterns, you can adjust the fabric
design accordingly, such as by adding, removing, or reconfiguring ISLs and trunking groups in
problem areas.
There are three methods of monitoring fabric traffic:
• Advanced Performance Monitoring monitors traffic flow and allows you to view the effect of different
fabric configurations on performance. See ”Administering advanced performance monitoring” on
page 343 for additional information.
• Fabric Watch allows you to monitor traffic flow through specified ports on the switch and send alerts
when the traffic exceeds or drops below configured thresholds. See the Fabric Watch Administrator’s
Guide for additional information.
• Use the portPerfShow command as described in the following procedure to record traffic volume for
each port in your fabric over time.