Patent ID: 7809884

Claim:
In a data storage system, a method of providing access to data, the method comprising: providing a disk mirroring assembly including a primary mirror and a secondary mirror, the primary mirror having a set of high speed disk drives, each high speed disk drive being configured to provide data access while rotating platters at a predefined high performance speed, the secondary mirror having a set of moderate speed disk drives, each moderate speed disk drive being configured to provide data access while rotating platters at a predefined moderate speed which is less than the predefined high performance speed; operating the disk mirroring assembly in a particular power management state; and performing data access operations on the disk mirroring assembly while the disk mirroring assembly operates in the particular power management state; wherein the predefined high performance speed is a maximum operating speed at which each high speed disk drive is configured to read and write data; wherein the predefined moderate performance speed is a maximum operating speed at which each moderate speed disk drive is configured to read and write data; wherein the disk mirroring assembly is configured to operate within a variety of power management states over time including: a “full active” mode in which (i) the platters of each high speed disk drive of the primary mirror continuously rotate at the predefined high performance speed and (ii) the platters of each moderate speed disk drive of the secondary mirror continuously rotate at the predefined moderate speed, an “active standby” mode in which (i) the platters of each high speed disk drive of the primary mirror continuously rotate at the predefined high performance speed and (ii) the platters of each moderate speed disk drive of the secondary mirror spin up and spin down in response to certain data access operations, and a “low power read” mode in which (i) the platters of each high speed disk drive of the primary mirror continuously rotate at the predefined high performance speed and (ii) the platters of each moderate speed disk drive of the secondary mirror remain spun down; wherein operating the disk mirroring assembly in the particular power management state includes: running the disk mirroring assembly in one of the “full active” mode, the “active standby” mode and the “low power read” mode at a particular point in time; and wherein performing data access operations on the disk mirroring assembly includes: processing high-priority read requests in the primary mirror, processing low-priority write requests in both the primary mirror and the secondary mirror, and processing low-priority read requests in the secondary mirror, while running the disk mirroring assembly in the “full active” mode.