Patent ID: 8037273

Claim:
A storage system connected to a host computer, comprising a plurality of disk drives and a controller to control the plurality of disk drives, wherein the plurality of disk drives include a first disk drive group including at least one disk drive, and a second disk drive group including the disk drives the number of which is larger than that in the first disk drive group, the host computer is provided with a logical volume including a plurality of logical storage areas, information indicating that one of a first attribute and a second attribute is assigned to the logical volume is held, when a new first logical volume including a plurality of first logical storage areas is provided to the host computer, the first attribute or the second attribute is assigned to the first logical volume, when the first attribute is assigned to the first logical volume, a plurality of physical storage areas of the first disk drive group are reserved as first logical storage areas, and when a write request is issued from the host computer, the plurality of first logical storage areas included in the first logical volume are allocated as storage areas for storing data requested to be written by the host computer, and the data requested to be written by the host computer are stored in the plurality of physical storage areas of the first disk drive group in which the plurality of the allocated first logical storage areas are reserved, when the second attribute is assigned to the first logical volume, a plurality of physical storage areas of the second disk drive group are reserved as the plurality of first logical storage areas, and when a write request is issued from the host computer, the plurality of first logical storage areas included in the first logical volume are allocated as storage areas for storing data requested to be written by the host computer, and the data requested to be written by the host computer are stored in the plurality of physical storage areas of the second disk drive group in which the plurality of the allocated first logical storage areas are reserved.