Energy Reduction for High Speed Disk Drives
Original Publication Date: 2002-Jun-03
Included in the Prior Art Database: 2003-Jun-21
HDD power consumption is a very strong function of the disk rotational speed (rpm). Therefore, it would be beneficial from a power standpoint to reduce spindle speed during idle times. However, without modification the drive would not be able to read before the drive reaches full rpm again. This would cause significant performance loss. If such loss is unacceptable for the particular drive design, then the read algorithms are modified to improve "file ready" times. As an example of the power savings that can be obtained, we list the relative contribution of spindle power with speed: 10k rpm: Pramp 0.5W 53% 12k rpm: Pramp 0.8W 85% 15k rpm: Pramp 0.95W 100% A second method to reduce the power consumption is based on burnishing the disk before the HDD leaves the factory. This can save 10% power spindle power. This effect was demonstrated during long term testing. The spindle current was monitored (figure below) while the drive was operational and the heads were sweeping (burnishing) over the disks. During the first 100 hours the current is significantly higher, indicating run-in. This run-in time is not consistent with normal motor grease channeling, which takes place during the first 10-15 hours of spinning; the drop was shown to be consistent with a change in disk morphology.