DISK ARRAY CONTROLLER, DISK ARRAY DEVICE AND DISK ARRAY CONTROL PROGRAM

PROBLEM TO BE SOLVED: To reduce a load of a master logical unit in the period of copy processing required to synchronize a backup logical unit with the master logical unit. SOLUTION: When a synchronization of a master logical unit LU210-0 and a backup logical unit LU210-1 is stopped at t1, snapshot data are taken in to the LU210-1. When a synchronization of the master logical unit LU210-0 and a backup logical unit LU210-2 is stopped at t2 later, the snapshot data are taken in to the LU210-2. When a resynchronization of the backup LU 210-1 is instructed further later, a controller 22 copies a part of D1-D2 of the D1 from the backup LU210-2 to the backup LU210-1 where D1 is an assembly of data written in the master LU210-0 from tl to the present as shown in a table DT1, and D2 is an assembly of data written in the master LU210-0 from t2 to the present as shown in a table DT2. COPYRIGHT: (C)2005,JPO&NCIPI