Provided is a computer system, including: a computer; and a storage system coupled to the computer via a network. The computer includes: an interface coupled to the network, a processor coupled to the interface and a memory coupled to the processor. The storage system includes a plurality of volumes in which files are stored. The processor is configured to: decide duplicating files from among the files stored in the plurality of volumes as files to be consolidated; identify a plurality of volumes in which the files to be consolidated are stored; select at least one volume from among the identified plurality of volumes as a consolidation volume based on loads imposed on the identified plurality of volumes; and delete the files to be consolidated stored in the volumes that are not selected. Accordingly, in data de-duplication, it is possible to avoid extra loads from centralizing in a high-load-bearing volume.