FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DC-TE, June 2003)

Physical Planning Considerations
143SAN High Availability Planning Guide
The figure illustrates two Director 2/64 directors connected by two ISLs. Three
servers use the ISLs to communicate with two storage devices. Without trunking,
servers 1 through 3 route Fibre Channel traffic to director B without regard to any
data rates. A possible scenario is that servers 1 and 2 route high data rate traffic
through ISL 1 to storage device 1 (ISL oversubscription) and server 3
routes low data rate traffic through ISL 2 to storage device 2
(ISL undersubscription).