Implementations of the present disclosure relate to a method, system and computer program product for managing a storage system. Specifically, in one implementation of the present disclosure there is provided a method for managing a storage system. The method comprises: dividing a source device among a plurality of storage devices in the storage system into a plurality of extents; copying data in the plurality of extents to a destination device; determining the state of an extent among the plurality of extents on the basis whether data in the extent among the plurality of extents has been copied to the destination device; and managing an access request to the extent on the basis of the state of the extent. In other implementations of the present disclosure, there is provided a corresponding system and computer program product.