IBM TotalStorage DS300 Best Practices Manual page 462

Zone
Zone4
Note: Although in this configuration a controller failover for an array is less
often necessary compared to "Fabric attachment with dual paths" on
page 440, it is recommend that logical drives within an individual array be
assigned only to a single host system.
Fabric attachment with quad paths without interswitch link
This configuration provides four paths from a host system to the DS400. In the
event of an outage of a HBA or its connection to the SAN switch the host system
can use a second path to controller in the DS400, preventing a failover for the
array.
444
IBM TotalStorage DS300 and DS400 Best Practices Guide
Initiator
Host2_HBA2
Targets
DS400_ControllerA_FC1
DS400_ControllerB_FC1