HP StorageWorks Fabric OS 6.x administrator guide (5697-7344, March 2008)

Fabric OS 6.x administrator guide 379
• Determine the optimal number of trunking groups between each set of linked switches, depending on
traffic patterns and port availability.
The goal is to avoid traffic congestion without unnecessarily using ports that could be used to attach
other switches or devices. Consider these points:
• Each physical ISL uses two ports that could otherwise be used to attach node devices or other
switches.
• Trunking groups can be used to resolve ISL oversubscription if the total capability of the trunking
group is not exceeded.
• Consider how the addition of a new path will affect existing traffic patterns:
• 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 you unlock the ISL Trunking license, you must reinitialize the ports being used for ISLs so that they
recognize that trunking is enabled. This procedure only needs to be performed one time.
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. Enter the switchDisable command.
3. Enter the switchEnable command.
To disable and re-enable ports:
1. Connect to the switch and log in as admin.
2. Enter the portDisable command. The format is:
portDisable [slot/]port
On directors, slot is the slot number and port is the port number of the port you want to disable.
3. Enter the portEnable command.The format is:
portEnable [slot/]port
On directors, slot is the slot number and port is the port number of the port you want to enable.
Monitoring traffic
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.