1. A storage system, comprising: a memory configured to store command history information that comprises a history of commands; an interface configured to receive a command from a computer; and a controller configured to: create, as a group, a relationship between a plurality of areas storing a plurality of data accessed by the command; manage the plurality of data of the plurality of the areas at a same access level based on the relationship, wherein the group is formed from the plurality of areas based on the command history information; and migrate the plurality of data of the plurality of the areas as a group between tier storage pools based on the same access level.