Storage system and data management method

A data management method performed in a storage system including a plurality of controllers, and a storage apparatus accessed by the plurality of controllers, data management of a storage area in the storage apparatus being assigned to one of the plurality of controllers, the data management method comprising:

• managing, by a first controller, first mapping information for accessing data stored in a storage area, management of which is assigned to the first controller, and second mapping information for accessing data stored in a predetermined storage area, management of which is assigned to a second controller,
• changing, by the second controller, when having executed garbage collection on the predetermined storage area, mapping information for accessing the data stored in the predetermined storage area to post-migration mapping information for accessing data after migration by the garbage collection, and
• acquiring, by the first controller, the post-migration mapping information from the second controller, and updating the second mapping information by using the post-migration mapping information in a case where information that is in the second mapping information and is to be used for accessing the data in the predetermined storage area has been updated accompanying the garbage collection when the first controller accesses the data in the predetermined storage area after the garbage collection by using the second mapping information.