Patent ID: 8166241
Filing Date: 2012-04-24
Classification: G06F

Abstract:
1. A computer system, comprising: a host computer; a first storage system coupled to the host computer through a network; and a second storage system coupled to the first storage system through the network, wherein: the first storage system comprises: at least one first interface coupled to the network; a first processor coupled to the at least one first interface; and at least one first disk drive configured to store data requested to be written from the host computer, and configured to set a first virtual volume, including a plurality of first virtual storage areas, recognized by the host computer as a logical volume and related to a plurality of first real storage areas; wherein: the first storage system includes an allocation bitmap indicating whether one of the first real storage areas in the first disk drive is allocated to one of the first virtual storage areas, and if the first virtual volume receives data from the host computer, and the first real storage area is not allocated to one of the first virtual storage areas in the first virtual volume, the first processor allocates the first real storage area to the first virtual storage area for storing data; wherein the second storage system comprises: at least one second interface coupled to the network; a second processor coupled to the at least one second interface; and at least one second disk drive configured to store data transferred from the first storage system, and configured to set a second virtual volume as a copy pair of the first virtual volume, including a plurality of second virtual storage areas related to a plurality of second real storage areas; wherein: the second storage system includes a differential information map indicating whether data is written in one of the second virtual storage area when the copy pair is in a suspend state, the first processor decides whether one of the first real storage areas is allocated to each of the first virtual storage areas on the basis of the allocation bitmap, and, if it is decided that one of the first real storage areas is allocated to one of the first virtual storage areas, data stored in the first real storage area allocated to the first virtual storage area is transferred to the second storage system through the first interface, if the second storage system receives data from the first storage system, and one of the second real storage areas in the second disk drive is not allocated to the second virtual storage area in the second virtual volume corresponding to the first virtual storage area, the second processor allocates one of the second real storage areas to the second virtual storage area for storing the transferred data; and when a copy process from the first virtual volume to the second virtual volume is executed, the first processor receives information from the differential information map of the second storage system to decide whether data is written in the second virtual storage area when the copy pair is in a suspend state, if data is written in the second virtual storage area when the copy pair is in the suspend state, the first processor decides whether the first real storage area is allocated to the first virtual storage area corresponding to the second virtual storage area on the basis of the allocation bitmap, and if the first real storage area is not allocated to the first virtual storage area corresponding to the second virtual storage area, the first processor instructs the second storage system to release the second real storage area allocated to the second virtual storage area.