Trunking Groups; Trunking Isls; Trunking Ports - HP StorageWorks MSA 2/8 - SAN Switch User Manual

Introducing ISL Trunking
ISL Trunking reduces or eliminates situations that require static traffic routes and
individual ISL management in order to achieve optimal performance. If any static
routes are specified using the urouteconfig command, the command
overrides the dynamic load sharing employed by ISL Trunking, and performance
may decrease accordingly.
ISL Trunking uses deskew values, which are a measure of the latency differences
between ISL cables in the same group, to provide in-order delivery of traffic.
Deskew values are automatically calculated at the creation of each new trunking
group.

Trunking Groups

A trunking group can contain two to four ISLs. If any eligible ISLs exist, trunking
groups automatically form when the ISL Trunking license is activated. Multiple
trunking groups can exist between the same two switches, and each switch can
support as many trunking groups as allowed by the available ports.

Trunking ISLs

The first ISL discovered in any trunking group is automatically designated as the
Trunking Master ISL. Each trunking group has one Master ISL and up to three
Subordinate ISLs. The Master ISL cannot be specified by the user.
If a Master ISL fails or is removed, there is a pause in the I/O associated with that
trunk as a new Master ISL is designated and traffic is redistributed. If data frames
were in flight during failure of the Master ISL, some frames may be lost,
depending on the Fibre Channel class; Class 2 frames are resent and Class 3
frames are dropped. The impact of any dropped frames on the I/O depends on the
host, application, storage, and host bus adapter (HBA) in use.
If a Subordinate ISL fails or is removed, the traffic is redistributed without
interruption over the remaining members in the trunking group.
The difference in cable length between the shortest ISL and the longest ISL in a
trunking group must be less than 400 meters, and less than 30 meters is
recommended.

Trunking Ports

The ports on either end of the Master ISL are called Trunking Master Ports, and
these ports work together to direct traffic over the trunked ISLs. All other ports are
called Trunking Subordinate Ports.
16 ISL Trunking Version 3.1.x/4.1.x User Guide