An active-active storage system, comprising a first storage array , a second storage array , and an address assignment apparatus , wherein the first storage array comprises a first source logical unit number, LUN , the second storage array comprises a first target logical unit number, LUN , and the first source LUN and the first target LUN are a pair of active-active LUNs, characterized in the storage system: the first storage array is configured to send (S502) an assignable-address set of the first source LUN to the address assignment apparatus, wherein the assignable-address set of the first source LUN comprises a plurality of assignable addresses of the first source LUN; the second storage array is configured to send (S504) an assignable-address set of the first target LUN to the address assignment apparatus, wherein the assignable-address set of the first target LUN comprises a plurality of assignable addresses of the first target LUN; the address assignment apparatus is configured to obtain (S505) a valid address from the assignable-address set of the first source LUN and the assignable-address set of the first target LUN, wherein the valid address is one assignable address in an intersection of the plurality of assignable addresses of the first source LUN and the plurality of assignable addresses of the first target LUN; and the address assignment apparatus is further configured to send (S506) the valid address to the first storage array, wherein the valid address will be used as an address of the first source LUN , after the first storage array binds the valid address to the first source LUN , and send (S508) the valid address to the second storage array, wherein the valid address will be used as an address of the first target LUN , after the second storage array binds the valid address to the first target LUN . the first storage array is configured to send (S502) an assignable-address set of the first source LUN to the address assignment apparatus, wherein the assignable-address set of the first source LUN comprises a plurality of assignable addresses of the first source LUN; the second storage array is configured to send (S504) an assignable-address set of the first target LUN to the address assignment apparatus, wherein the assignable-address set of the first target LUN comprises a plurality of assignable addresses of the first target LUN; the address assignment apparatus is configured to obtain (S505) a valid address from the assignable-address set of the first source LUN and the assignable-address set of the first target LUN, wherein the valid address is one assignable address in an intersection of the plurality of assignable addresses of the first source LUN and the plurality of assignable addresses of the first target LUN; and the address assignment apparatus is further configured to send (S506) the valid address to the first storage array, wherein the valid address will be used as an address of the first source LUN , after the first storage array binds the valid address to the first source LUN , and send (S508) the valid address to the second storage array, wherein the valid address will be used as an address of the first target LUN , after the second storage array binds the valid address to the first target LUN . <EOS>