The subsystem device driver (SDD) for Windows® supports dynamic pathing for hosts that run some versions of the Windows 2000 Server and Windows Server 2003 operating systems.
SDD supports dynamic pathing when you add more paths to an existing VDisk and when you present a new VDisk to the host. No user intervention is required, other than is normal for a new device discovery under the Windows operating system.
SDD uses a load-balancing policy and tries to equalize the load across all preferred paths. If preferred paths are available, SDD uses the path that has the least I/O at the time. If SDD 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.