Disk drive and method of controlling cache memory therein

A method of controlling a cache memory in a disk drive, comprising:

• extracting a pattern of processing requests in which read requests making access to a space located within a given distance in the positive direction of logical block addresses (LBAs) on a disk repeatedly alternate with write requests making access to continuous or non-continuous areas in the LBA space;
• setting a position at which data about writing is started to be written to the cache memory, based on the ratio of the amount of data transferred to the cache memory during reading to the amount of data transferred to the cache memory during writing;
• executing cache control for the pattern of processing requests;
• making a decision as to whether the pattern of processing requests persists when a new processing request is received;
• making a decision as to whether data about writing has been just written to the disk if the decision at the immediately preceding step is YES;
• executing the cache control for the pattern of processing requests unless the data about writing has been just written to the disk;
• and
• resetting the position at which data about writing is started to be written to the cache memory if the data about writing has been just written to the disk;
• wherein making a decision as to whether the pattern of processing requests persists when the new processing request is received includes:
• performing a check as to whether each processing request is a read request;
• performing a check as to whether there is any access to the final LBA of data required by the immediately preceding read request located within a given distance from the final LBA in the positive direction if the decision at the immediately preceding step is YES;
• and
• determining the pattern of the processing request as persisting if the decision at the immediately preceding step is YES.