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Baked-In Power Benefits
The dichotomy of “performance or low-power” has been stated so often that it’s easy to forget how much performance drives continue to benefit from low-power innovations. Again, consider CPUs as an example. Without increasing the thermal design power (TDP) envelope, Intel and AMD now deliver several times as much compute performance as they did with CPUs of years past. Power efficiency continues to increase.
Conventional hard drives have three power-saving modes: Idle, Sleep and Standby. These are part of the ATA command set and depend on instructions issued by the host controller. Idle mode kicks in a few seconds after active reading and writing finishes. The head gets parked and some drive electronics shut down, but the platters continue rotating for a very quick response time when new commands arrive. Standby mode parks the head and spins down the platters while still keeping the drive electronics active. Sleep mode powers down even more of the electronics, thus requiring a drive reset before the host can control it.
In addition, hard drives also have Advanced Power Modes (APMs) that can be implemented by timers independent of the host. The three idle APMs are:
Idle 1: The drive head is flying but not seeking and disks are spinning at full speed.
Idle 2: The head is parked and the disks are still spinning at full speed.
Idle 3: The head is parked and the disks are not spinning. This is the same as standby mode, but the condition was initiated by the drive rather than the controller.
More recently, some drive manufacturers, including Seagate in its Barracuda line, implemented a “ramp load” mechanical design as opposed to the older “contact stop-start” design. Ramp load allows for a variation of Idle 3 in which the head is parked but the platters continue spinning at a reduced spindle rate. This is a compromise approach, allowing the drive to spin up faster yet consume less power during wait times.
There are even more energy-saving enhancements in the enterprise market collectively called Extended Power Management (EPM). These will doubtless filter down in one form or another into the consumer market and make mainstream drives even more efficient. And don’t forget that hybrid drives, combining the best of magnetic hard drive and solid state flash technologies, will continue to become more common and affordable. Seagate already offers the hybrid approach in its Momentus XT line and will soon transition the Barracuda XT line. Since hybrids can handle many frequent data requests without spinning up the platters, expect power efficiency gains here to be significant, as well.