HP Array Controller HSG V8.7 Software - Manual (Page 302)

B–30 HSG80 User’s Guide
The MAXIMUM_CACHED_TRANSFER switch affects both read and
write-back cache when set on a controller that has read and write-back
caching.
PREFERRED_PATH=OTHER_CONTROLLER
PREFERRED_PATH=THIS_CONTROLLER
NOPREFERRED_PATH (Default)
May be set only when dual-redundant controllers are operating in a
multiple bus failover configuration. In a multiple bus failover
configuration, the host determines which controller the units are
accessed through. The host’s unit-to-controller settings always take
precedence over the preferred path assigned to units with this switch.
The target ID numbers assigned with the SET controller
PORT_1_ALPA= (or PORT_2) command determines which target ID
number the controller uses to respond to the host.
Note If your controllers are configured to operate in transparent-
failover mode, do not set the PREFERRED_PATH switch with the
ADD UNIT or SET unit-number command—otherwise, an error
message is displayed. The error message indicates the assignment of a
preferred controller path at the unit level is valid only when operating
in multiple bus failover mode.
When no preferred path is assigned, the unit is targeted through the
controller which detects the unit first after the controllers start.
Select PREFERRED_PATH=THIS_CONTROLLER to instruct “this
controller” to bring the units online.
Select PREFERRED_PATH=OTHER_CONTROLLER to instruct the
“other controller” to bring the units online.
See Chapter 2 for information regarding multiple bus failover.
Tip Subsystem performance is better if target ID numbers are
balanced across the dual-redundant pair.