Abstract: A storage path driver(SPD) is proposed and implemented to provide dynamic load balancing across multiple I/O paths between the hosts and the storage subsystems.I/O requests bound for the LUNs(logical units) are dispatched to parallel physical paths by the SPD driver to distribute the host load to the storage network. The multiple server congregation model from queue theory is applied to analyze the relationship between the overall throughput and several factors,such as the host load,number of host bus adapters(HBAs) and HBAs' performance.The load balance algorithm based on HBAs is implemented to increase the I/O throughput and shorten the average I/O response time.