1. A computer-readable storage medium storing a load balancing program for use in a storage system including a plurality of storage nodes interconnected by a network and storage devices coupled to each storage node, the load balancing program, when executed on a computer, causing the computer to function as an apparatus comprising: a management data storage unit to store management data describing association between logical segments and physical segments, wherein the logical segments are virtual storage areas with a specified segment size into which a logical volume is divided, and wherein the physical segments are real data storage areas with the specified segment size into which storage space of the storage devices is divided; a segment identification unit, responsive to access requests directed to an access range of the logical volume, to identify the physical segments associated with the logical segments in the specified access range of the logical volume, based on the management data; a remapping unit to subdivide the logical segments in the access range into logical sub-segments with a specified sub-segment size, as well as the physical segments associated therewith into physical sub-segments with the specified sub-segment size, and to remap the logical sub-segments to the physical sub-segments according to a predetermined remapping algorithm; and a data access unit to execute the access requests based on the remapped logical sub-segments and physical sub-segments.