Patent ID: 6959359

Claim:
An external storage system comprising: a plurality of disk drives for storing data; a drive interface control unit operatively couple to the disk drives; a channel interface control unit through which a connection with a supervisory unit can be established for reading and writing data; a cache memory connected to the drive interface control unit and to the channel interface control unit, the cache memory for temporarily storing data between the disk interface control unit and the channel interface control unit; and a shared memory connected to the drive interface control unit and to the channel interface control unit, the shared memory for storing information relating to data that is to be staged to the cache memory, the information being used by the channel interface control unit to stage data that is stored in a plurality of tracks in one or more of the disk drives to the cache memory by way of the drive interface control unit, the information further being used by the channel interface control unit to destage data from the cache memory to be stored to the disk drives by way of the drive interface control unit, wherein staging of the data to the cache memory and destaging of the data from the cache memory are performed according to staging and destaging instructions from the supervisory unit, the instructions formulated by the supervisory unit according to criteria provided by a user.