HP StorageWorks 2000 Series Reference Manual page 265

The SAS storage system uses Unified LUN Presentation (ULP). ULP is a controller
software feature that enables hosts to access mapped volumes through both
controllers' host ports (target ports) without the need for internal or external
switches.
In a dual-controller SAS system, both controllers share a unique node WWN so they
appear as a single device to hosts. The controllers also share one set of LUNs to use
for mapping volumes to hosts.
A host can use any available data path to access a volume owned by either
controller. The preferred path, which offers slightly better performance, is through
target ports on a volume's owning controller.
Ownership of volumes is not visible to hosts. However, in SMU you can
view volume ownership and change the owner of a virtual disk and its volumes.
In the following configuration, both hosts have redundant connections to all mapped
volumes.