The storage system provides a logical volume and includes a plurality of disk devices and a controller, coupled to the plurality of disk devices, which manages a plurality of storage areas provided by the plurality of disk devices. There can be provided a symmetric hyperbranched silicone-modified polymerizable compound having a structure with chemically high flexibility at the branched chain, having good reactivity of the polymerizable functional group, and having a branched structure which is positionally and sterically symmetric and pure than the conventional ones. Non-uniform tessellation may be applied to only a portion of the base object, and regular tessellation may be applied to the other portion. Embodiments of joints are provided with a simple design that is inexpensive to manufacture.