<p>Provided are a computer system and a data migration method that can substitute storage devices while avoiding stopping data transmission and reception between a host computer and the storage devices, without relying on the configuration of existing storage devices, etc. Within the computer system comprising the host computer and first and second storage devices: the second storage device virtualizes first logical units within the first storage device and provides same to the host computer as second logical units, collects configuration data for each first logical unit, and sets each collected configuration data to the associated second logical units; the host computer adds paths to the second logical units and deletes paths to the first logical units; and the second storage device copies data stored in the first logical units to a memory area provided by a second memory device and associates said memory area to the second logical units.</p>
