Patent ID: 6981115

Claim:
A storage system arranged to be coupled with a backup device and a computer, comprising: a first storage unit; a second storage unit storing a copy of data stored in said first storage unit; and a storage control device coupled with said computer for controlling access to said first storage unit and said second storage unit, wherein said storage control device updates data stored in said first storage unit in response to an update request from said computer and copies updated data stored in said first storage unit to said second storage unit, in response to receipt thereby of a split instruction from said computer, said storage control device stops copying updated data stored in said first storage unit to said second storage unit after receiving said split instruction, in response to receipt thereby of a copy instruction including specification of a logical volume stored in said second storage unit from said computer, said storage control device checks whether the specified logical volume is stored in said second storage unit and whether the split instruction has been executed for the specified logical volume, and based on the check, said storage control device reports an error to said computer and then the execution of said copy instruction is canceled, or transfers data stored in the specified logical volume in said second storage unit into said backup device directly, without using said computer.