Patent ID: 7085965

Claim:
An apparatus in which an arbitrary sector in an alternate area of a disk is allocated as an alternate sector to a defective sector on the disk, comprising: an alternate sector buffer which stores data corresponding to data written in the alternate sector allocated to the defective sector; a data buffer which temporarily stores data read from the disk and to be transferred to a host using the apparatus, and data transferred from the host and to be written to the disk; a buffer access circuit which copies data between the alternate sector buffer and the data buffer; and a disk access controller which controls disk access requested by a read/write command supplied from the host, during the disk access, data being transferred between a disk access range on the disk designated by the read/write command and the data buffer, the disk access controller suspending the disk access if the disk access range contains the defective sector and a head used to read/write data to the disk reaches the defective sector, the disk access controller causing, during suspension of the disk access, the buffer access circuit to copy data between an area of the alternate sector buffer and the data buffer, the area of the alternate sector buffer storing the data corresponding to the data written in the alternate sector allocated to the defective sector that is contained in the disk access range.