1. A management computer comprising: a memory; and a processor coupled to a storage system that provides a first volume as a logical volume that stores a first image of an object and to the memory, wherein the processor: recognizes a state of the storage system; based on the state, selects one generation processing from a plurality of generation processing including: first generation processing, executed by the storage system, of generating a second volume as a virtual logical volume that stores a second image of the object and associating the second volume with the first image and differential data from the first image to provide the second volume; and second generation processing, executed by the storage system, of generating the second volume as a logical volume and copying the first image to the second volume to provide the second volume; and transmits an instruction to execute the selected generation processing to the storage system.