Facebook's Open Compute Project has a post by Eran Tal on HDD Power Savings.
One of comment responses is from a Western Digital employee.
Brandon SmithAug 20I work at Western Digital, the largest disk drive producer in the world on motor control, and this is already being implemented. I am not sure how many drives this has already been shipped with, but we definitely have low RPM standby modes. I believe it might take a few hundred ms to get back up to speed and load the heads to get to the data, so if the latency requirement is less than 100 ms, I am not sure this strategy is the way to go for data centers. Also, a spindle motor designed to spin at 7200 RPM will not spin efficiently or consistently at 3600 RPM. 4500 to 5000 RPM is a more realistic number.
For this type of storage, SSD's are not the answer, because they are not even close to cost competitive. HDD's are the way to go, but we need to be realistic about the time it will take to access the data if we want to save energy.
So what Green Technologies does WDC?
IntelliSeek.Calculates optimum seek speeds to lower unnecessary power consumption, noise, and vibration. View demoIntelliPower.A fine-tuned balance of spin speed, transfer rate, and caching algorithms designed to deliver both significant power savings and solid performance. Additionally, drives with WD GreenPower Technology consume less current during start up allowing more drives to spin up simultaneously resulting in faster system readiness.IntelliPark.Delivers lower power consumption by automatically unloading recording heads during idle to reduce aerodynamic drag, and by disengaging read/write channel electronics.Active Power Management.Drives with WD GreenPower Technology monitor the work load and automatically invoke idle mode whenever possible to further reduce unnecessary power consumption. Drive recovery time from idle mode is less than one second, providing seamless power management between the drive and the host controller.Ideal for:Large data centers, web service providers, commercial grade surveillance systems and organizations requiring huge amounts of storage with limited budget and power allotment.