Each new generation of drives offers better capacity and performance but is generally using less power -- both at spin up and during normal operation. It's important to avoid focusing on the individual drives. For example, small form factor drives are drawing less power but allow more drives to be packed into the same physical area. You may find that the total power demands of your new high-density array are greater, even though each individual drive may use considerably less power. Several large drive arrays already incorporate some form of drive power management at the system level, though the most interest is in managing power autonomously at the individual drive level, including different power modes. Also, look at the over all effectiveness of the drives and the storage controller to increase performance while reducing drive power consumption as opposed to simply looking at gigabytes of storage per unit of electrical power (watts).
Hybrid drives using substantial amounts of onboard RAM
or flash memory
to cache platter contents are particularly interesting in terms of power management. When the physical hard drive isn't actually needed, its contents have already been cached to onboard memory; the drive could operate at reduced revolutions per minute or spun down completely. Meanwhile, the drive's data is accessed from the onboard memory. When the needed data is not in memory, the drive is spun up and the platters are accessed.
Still, spin-up power remains an important issue. It's possible to spin down numerous drives and save substantial running power, but spinning up a large number of drives simultaneously can produce a significant surge in power demands. Frequent starts and stops may also have an adverse effect on long-term drive reliability. Consequently, a trend is to use multiple power modes on disk drives to vary performance and power consumption while prolonging disk drive use.
Go back to the beginning of the Disk Hardware FAQ Guide.
08 May 2007