Patent ID: 6985998
Filing Date: 2006-01-10
Classification: G06F,G11B

Abstract:
1. A disk array device that provides a host device with required data in accordance with a data read request from the host device, comprising: a plurality of disk drives that belongs to at least one parity group, each disk drive of which starts idle seek, unless data access is taking place, when a period equal to or more than a first threshold value period has elapsed from the time the previous idle seek ends; a disk interface for communicating with the disk drives; a host device interface for communicating with the host device; and a control device that is connected to the disk interface and the host device interface and controls the disk array device, wherein the control device comprises: a time monitoring unit which has ON or OFF status information for each of the plurality of disk drives and alternately switches the status information of each disk drive ON and OFF, such that, in cases where a period equal to or more than a second threshold value period shorter than the first threshold value period has elapsed after switching the status information of each of the disk drives from ON to OFF, when the status information of all the other disk drives belonging to the same parity group as each of the disk drives is OFF, the status information of each of the disk drives is switched from OFF to ON, and then, once the idle seek of each of the disk drives has ended, the status information of each of the disk drives is switched from ON to OFF; an idle seek start prediction unit that detects in advance a disk drive that is predicted to start idle seek; a multiple idle seek prevention unit, which, in cases where a period equal to or more than the second threshold value period has elapsed after switching the status information of each of the disk drives from ON to OFF, prevents each of the disk drives from starting idle seek by performing dummy access with respect to each of the disk drives when the status information of any of the other disk drives belonging to the same parity group as the disk drives is ON; and a data access control unit which, in cases where required data is read from the disk drive in response to the read request from the host device, when the status information of a target disk drive where the required data is stored is OFF, sends the required data to the host device by reading the required data from a target disk drive and, when the status information of the target disk drive is ON, recovers the required data by reading data from all the other disk drives belonging to the same parity group as the target disk drive without performing data access with respect to the target disk drive, and then sends the required data thus recovered to the host device, wherein when the predicted disk drive that is predicted to start idle seek is detected by the idle seek start prediction unit, if another drive within the same parity group as the predicted disk drive is executing idle seek, the multiple idle seek prevention unit performs dummy access with respect to the predicted disk drive so that the predicted disk drive does not start idle seek.