Multipathing drivers provide three basic features: Failover.
This includes detection of link failure and automatic rerouting to alternate path. Different HBA drivers provide different levels of transparency to the OS and application.
Load-balancing.
Some multipathing drivers allow you to manually determine which LUNs are accessed over which HBA ports, while others provide automatic path selection capability. This is basic load-levelling. More advanced multipathing software provides actual load- balancing—dynamic levelling of traffic flows on a per-flow or per- Exchange basis.
Administration.
Multipathing software can provide intelligent path selection capability, dynamic configuration, and centralized administration of multiple hosts from one console.