Information technology (IT) managers are faced with ever-growing needs for additional data storage space. Until recently, additional storage solutions involved adding more hard drives, but this results in more energy being consumed, more heat being generated, and higher utility bills. The additional heat often requires IT managers to purchase additional cooling systems and data-center power supplies. An alternative solution to just adding hard drives is using Massive Arrays of Idle Discs (MAID), a technology that powers down hard drives that are not in use at any given time. Because 90 percent of an enterprise's files are accessed only about 10 percent of the time, massive arrays of dormant disc drives can be shut off. A MAID system can save an IT department about 1,500 watts of electricity per 100 hard drives. There are other advantages to MAID besides energy savings, the most notable one being the possibility that it extends the lifespan of hard drives. MAID subsystems work basically the same as hard drives found in laptop computers, which power themselves down when not in use. Whereas laptop computers rely on the operating system to manage the idle hard drive's directory structure, MAID subsystems require a storage management system that maintains meta-files. The only company to release a MAID subsystem is Copan Systems. The Revolution 220T, and its cousin the Revolution 220A, both consist of a three-tiered RAID architecture that is divided into racks, shelves, and canisters. The Revolution 200 Series is used in conjunction with Copan's Disk Aerobics software.