Patent ID: 8661220

Claim:
A backup method for a computer system including a management computer, a first storage apparatus connected to the management computer, and a second storage apparatus connected to the management computer and the first storage apparatus, the method comprising: based on a read speed for a first storage area belonging to the first storage apparatus, a write speed for a second storage area belonging to the second storage apparatus, a write speed for a third storage area, which belongs to the second storage apparatus and whose write speed is faster than that of the second storage area, and an amount of differential data that is part of the data in the first storage area and that is not stored in the second storage area, calculating, by the management computer, a capacity of the third storage area to complete copying of the differential data within a specified period of time; and when a capacity of the third storage area is larger than the calculated capacity, copying, by the second storage apparatus, the differential data, which has been sent from the first storage area, to the second storage area or the third storage area and migrating the differential data, which has been copied to the third storage area, to the second storage area.