Patent ID: 8099569

Claim:
A storage system, comprising: a host apparatus equipped with a second copy function for reading data stored in a first volume of a first storage apparatus in file units from the first storage apparatus and copying the data to a corresponding second volume of a second storage apparatus; a controller equipped with a first copy function for controlling the first and second storage apparatuses to copy data stored in the first volume to the second volume in volume units; and a data migration control unit for deciding whether to migrate data stored in the first volume according to a first data migration method that migrates data in volume units or a second data migration method that migrates data in file units according to the status of data stored in the first volume to be subject to data migration, and executing necessary control processing so that data migration is performed according to the decided first or second data migration method; wherein the data migration control unit preferentially decides the first data migration method as the data migration method when the capacity of the first volume to be subject to data migration is greater than a first threshold value, a file system exists in the first volume, and the last update date and time of data stored in the first volume is older than a second threshold value, wherein the second threshold value is a date and time going back a predetermined period from a current date and time, and preferentially decides the second data migration method as the data migration method when the capacity of the first volume to be subject to data migration is greater than the first threshold value, a file system exits in the first volume, and the last update date and time of data stored in the first volume is newer than the second threshold value.