If you use the IBM subsystem device driver device-specific module (SDDDSM), you must also use the Microsoft Multipath I/O (MPIO) driver for dynamic pathing.
MPIO supports dynamic pathing when you add more paths to an existing volume and when you present a new volume to the host. No user intervention is required, other than the typical new device discovery on a Windows operating system.
SDDDSM uses a load-balancing policy that attempts to equalize the load across all preferred paths. If preferred paths are available, SDDDSM uses the path that has the least I/O at the time. If SDDDSM finds no available preferred paths, it tries to balance the load across all the paths it does find and uses the least active non-preferred path.
Path probing and reclamation is provided by MPIO and SDDDSM. For SDDDSM, the interval is set to 60 seconds. You can change this by modifying the following Windows system registry key: HKLM\SYSTEM\CurrentControlSet\Services\mpio\Parameters\PathVerificationPeriod