Even without a first storage system does not have compatibility with a second storage system that is different from a default cloud storage service which can be accessed by a cloud computer service as a migration destination of a computer instance, a volume in the first storage system can be migrated to the second storage system. A system causes a migration tool of a cloud computer to migrate, from a first storage system to the cloud computer, a system volume storing an image of an OS for configuring a computer instance to be migrated, and a data volume storing data used by the OS, and creates a mapping volume, which has been mapped to the data volume migrated to the cloud computer with the migration tool, in a second storage system, and sets a path of data input/output from the computer instance to the mapping volume in the computer instance.