Patent ID: 7260696

Claim:
A computer system comprising: a plurality of storage systems each of which comprises at least one logical unit and a control unit coupled to said at least one logical unit, and a computer comprising an application, said application configured to issue an access request to access data stored in a logical unit in a storage system of the plurality of storage systems, wherein said application is configured to issue an access request to access target data in a logical unit by using a first ID, and wherein a storage system of the plurality of storage systems comprises a logical unit configured to store said target data and access said target data by using a second ID of said logical unit, said second ID corresponding to said first ID, and wherein a source storage system of the plurality of storage systems is configured to receive a data reallocation command, and to transfer data stored in a source logical unit in said source storage system to a target logical unit in a target storage system of the plurality of storage systems based on the data reallocation command, wherein said target logical unit is determined based on characteristic information of logical units in said plurality of storage systems, wherein the first ID of the data transferred from said source logical unit is correlated with the second ID of the data received by said target logical unit to update correlation information between first IDs associated with access requests and second IDs associated with target data corresponding to the access requests in order to allow said application to access data in said target logical unit by using the same first ID as the first ID used by said application before data transfer from said source logical unit to said target logical unit.