Patent ID: 8892840

Claim:
A data migration method for migrating data from a first storage apparatus to a second storage apparatus in a computer system comprising: a computer; the first storage apparatus on which a first storage device is mounted and which manages first logical units provided by a storage area of the first storage device; and the second storage apparatus on which a second storage device is mounted, the data migration method comprising: a first step, executed by the second storage apparatus, of virtualizing each of the first logical units in the first storage apparatus, managing them as second logical units, and setting configuration information about the first logical units to corresponding second logical units; and a second step of adding a path to the second logical units as an alternate path target, causing a status of a path connected to the first logical units to change to a standby state without deleting a setting of the path connected to the first logical units, notifying the change of the status of the path connected to the first logical unit to the first storage apparatus, copying data stored in the first logical units in the first storage apparatus to a storage area provided by the second storage device, and associating the storage area with the second logical units under the control of the second storage apparatus, wherein after the completion of data copying between the first and second storage apparatuses, the computer deletes the path connected to the first logical units, wherein if data which has not been migrated from the first storage apparatus to the second storage apparatus is a target of a read request from the computer, the second storage apparatus converts the read request from the computer to a read request to the first storage apparatus and the first storage apparatus processes the read request, and if data stored in the second storage apparatus is a target of the read request, the second storage apparatus processes the read request.