IBM Midrange System DS4000 Series Hardware Manual page 238

With MPIO, each device listed here represents a logical drive. In order to display the different
paths of each one, select it and then choose Properties. Select the MPIO tab to display the
different paths to the DS5000 storage subsystem. From the same Properties window, you can
set the different Load Balance policies for the MPIO driver. Depending on the current physical
path state, and the policy selected, the paths are both Active (round robin, weighted paths), or
one Active and the other in Standby (failover, Least queue depth), as shown in Figure 4-88.
Figure 4-88 MPIO load balancing policy
Important: The Load Balance algorithms only work between multiple paths to the same
controller. If you only have one path, you can only have failover capability.
For a correct data assignment to your defined logical volumes, you need to determine which
of the disks drives in the Windows Device Manager or Disk Manager relates to the previously
defined logical volumes of your DS5000 storage subsystem.
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IBM Midrange System Storage Hardware Guide
Load Balance:
Only across paths
to the same controller
If only two paths:
One for A controller
and the other to B
controller, FAIL OVER
only algorithm