A data copy method for a disk sub system that is equipped with a first storage apparatus including a first logic storage apparatus divided into a first region and a second region and a second storage apparatus including a second logic storage apparatus divided into a first region and a second region, the first logic storage apparatus and the second logic storage apparatus connecting to a host apparatus, wherein data on the first logic storage apparatus is copied to the second logic storage apparatus by an instruction from the host apparatus. With the data copy method, the second logic storage apparatus is designated as a copy destination for copying data of the first logic storage apparatus, the second region of the first logic storage apparatus and the second region of the second logic storage apparatus are switched with one another, and data stored in the first region and the second region within the first storage apparatus are copied to the first region and the second region within the second storage apparatus.