HP A7533A HP StorageWorks Fabric OS 6.1.1 administrator guide (5697-0235, Dece - Page 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. Fabric OS 6.1.x administrator guide 369