HP StorageWorks 2.128 SAN Director Switch - Manual (Page 167)

Fabric OS 5.x administrator guide 167
12 Administering ISL trunking
This chapter contains procedures for using the HP ISL Trunking licensed feature, which optimizes the use
of bandwidth by allowing a group of ISLs to merge into a single logical link.
About ISL trunking
HP ISL Trunking reduces or eliminates situations that require static traffic routes and individual ISL
management to achieve optimal performance. Trunking optimizes fabric performance by distributing
traffic across the shared bandwidth of all the ISLs in a trunking group, allowing traffic to flow through any
available link in a group rather than restricting it to a specific, potentially congested link. The use of
trunking results in simplified fabric design and management, lowered cost of ownership, and increased
data availability.
To use trunking, you must first install the HP ISL Trunking license. For details on obtaining and installing
licensed features, see ” Maintaining licensed features ” on page 26. Trunking is enabled when the ISL
Trunking license is activated and ports are reinitialized (after installing the license, you issue the
switchDisable
and
switchEnable
commands). Trunks are easily managed using either Fabric OS
CLI commands or Advanced Web Tools. You can enable and disable trunking and set trunk port speeds
(for example, 2 Gig/sec, 4 Gig/sec, or auto-negotiate) for entire switches or for individual ports.
Trunks distribute traffic dynamically and in order at the frame level, achieving greater performance with
fewer ISLs.
Trunks are compatible with both short wavelength (SWL) and long wavelength (LWL) fiber optic cables
and transceivers.
Figure 4 illustrates how trunking can result in more throughput by distributing data over four ISLs with no
congestion. In a fabric that does not have trunking capability, some paths would be congested and other
paths underutilized.
Figure 4 Distribution of traffic over ISL trunking groups
Trunks operate best when the cable length of each trunked link is roughly equal to the others in the trunk.
Cable lengths for participating links should differ by no more than 550 meters. For optimal performance,
HP recommends no more than 30 meters difference.
Connections between the SAN Switch 4/32 and 4/256 SAN Director (using FC4-16 and FC4-32 port
blades) support these advanced features:
• Up to eight ports in one trunk group to create high-performance 32-Gbit/sec ISL trunks between
switches
• ISL trunking over longer distances than other models
• Dynamic trunk master reassignment if a trunk master is disabled (on other platforms, all ports on a
trunk must be disabled temporarily to reassign a master)
• 4 Gbit/sec trunk links