HP AA979A - StorageWorks SAN Switch 2/8V, Administrator'S Manual, Page: 353 / 465

Fabric OS 5.3.0 administrator guide 361
• 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 might 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
Slot
is the slot number (SAN Director 2/128 Director only) and
port
is the port number of the port
you want to disable.
3. Enter the
portEnable
command.The format is:
portEnable
[
slot
/]
port
Slot
is the slot number (SAN Director 2/128 and 4/256 SAN Director only) and
port
is the port
number of the port you want to disable.