Hard disk drive having buffer memory employing directory based cache

Abstract

A disk drive including a magnetic disk having a plurality of concentric tracks formed thereon and a plurality of blocks each having data recorded on the track and a block address, a buffer memory, divided into plural segments, for storing data retrieved from the disk in each of the buffer memory segments, and buffer memory controller for controlling the buffer memory. The buffer memory controller includes a directory storage memory for storing buffer memory address information in directory segments corresponding to the buffer memory segments, a replacement control information storage memory for storing in each directory segment information relating to a history of use of data for each buffer memory segment. The buffer memory controller determines whether target data are stored in one of the buffer memory segments based on information relating to the target data and the information stored in the directory storage memory, and updates the information stored in the replacement control information storage memory according to a prescribed replacement control rule. The disk drive further includes a data process controller for controlling the buffer memory controller accessing the data in the buffer memory.