HP StorageWorks 2000 Series Reference Manual page 260

The topology only affects how mapped volumes and port WWNs are presented if
one controller fails. Whichever topology is used, each data host has dual-ported
access to volumes through both controllers.
Failover in a switch attach, loop configuration. If one controller fails in a
switch attach configuration using loop topology, the host ports on the surviving
controller present the port WWNs for both controllers. Each controller's mapped
volumes remain accessible.
Failover in a switch attach, point-to-point configuration. If one controller fails
in a switch attach configuration using point-to-point topology, the surviving
controller presents its mapped volumes on its primary host port and the mapped
volumes owned by the failed controller on the secondary port.
In a high-availability configuration, two data hosts connect through two switches to
a dual-controller storage system and the host port interconnects are disabled.
The following figure shows how port WWNs and mapped volumes are presented
when both controllers are active.