Patent ID: 7350102

Claim:
A computer usable medium tangibly embodying a program of machine-readable instructions executable by a processor to perform operations to read information stored in a double mirror storage system comprising a controller coupled to a plurality of type I performance class disk drives and at least one type II performance class backup disk drive, wherein the type I performance class disk drives contain data blocks and parity blocks for the data blocks and wherein the type II performance class disk drives contain redundant data blocks and redundant parity blocks the operations comprising: executing a first read request for a first set of information from a first type I performance class disk drive, wherein the information constitutes segments of at least one of the data block and the parity block; determining a first read error associated with the execution of the first read request; and executing a second read request for the first set of information from a first type II performance class backup disk drive wherein the controller minimizes the use of the first type II performance class drive and maximizes the use of the first type I performance drive.