You may have not noticed one of the areas of research mentioned within the recent NetApp white paper, "Reducing Data Center Power Consumption Through Efficient Storage". While I believe most power savings come from software features, there's some pretty serious R&D work being put into intelligence control of the speed of individual drives in response to demand.
According to EUN (Energy User News), the power requirements of today’s data centers range from 75 W/ft^2 to 150-200 W/ft^2 and will increase to 200-300 W/ft^2 in the near future.
Look -- everyone's goal here is to conserve energy without sacrificing performance. But right now, enterprise storage systems are fairly "dumb"...basically consisting of 3 power states:
- active
- idle
- off
In active mode, the platters are spinning and the head is seeking or actively reading/writing. In idle mode, a disk is spinning at full speed but no disk activity is taking place. There's no "sleep" mode for enterprise storage system (unlike your laptop or desktop). Of course, spinning up from being powered-off incurs significant time and energy overhead at the moment.
Come to think of it, incandescent light bulbs are a lot like today's typical enterprise disk drives -- an inefficient dinosaur.
So imagine your storage system tends to be very underutilized between the hours of 6 pm to 12 am and 4 am to 8 am. The system would gather these metrics, analyze historic trends, and reduce the speed (or power down) specific disks during those off-peak hours in a bimodel distribution of busy & idle disks.
There's even research being put into "power-aware" RAID designs and extending hybrid hard drives into the enterprise space.
Wow, putting this together with using RAID-DP on ever-larger SATA drives, thin provisioning, FlexClones, Snapshots, de-duplication, automated data lifecycle policy engines, and consolidation of servers save some real dough.
