The present disclosure provides a method and an apparatus for a storage system. The storage system includes an active storage site and a standby storage site, and a logical unit number LUN for a storage pool of the active storage site is replicated to a LUN for a storage pool of the standby storage site to form a consistency group. The method comprises: creating a first LUN and a second LUN as mirrors of each other at the active storage site and the standby storage site, respectively; adding the mirrors formed by the first LUN and the second LUN to the consistency group; after the second LUN is added to the storage pool of the standby storage site, adding the first LUN to the storage pool of the active storage site.