Disk Drives

Power Efficiency Guide

Ultimate Guide to Power Efficiency

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Even though the CPU is necessary to accomplish much of anything on a computer, most of the data will ultimately be stored on and recalled from a disk drive. In a data storage center, depending on how data is stored, many disk drives may be simultaneously running. Each drive draws power. Done incorrectly, it wastes a large amount of power and costs the company a large amount of money.

Disk drives work by storing data on a set of flat rotating surfaces called a disk or platter. Spinning these platters is the main source of energy consumption. The disks spin at a very high speed. However, the speed at which the disks spin, as well as the other functions of the drive, can all be regulated to reduce power consumption with a relatively small, if any, degradation in read/write speed.

Because a data center stores so much information, it needs a large volume of storage media. If the data is simply being stored and seldom referenced, and it is OK to have a slow access time, then tape drives will suffice. Idle tape drives consume little power. However, when the data is expected to be needed relatively quickly and will be accessed often, it should be stored on a disk drive. If all disk drives in the center are spinning all the time, a large amount of power is constantly consumed. This activity also generates heat that must be dissipated or cooled. A rule of thumb in the data center is that one watt of power for equipment means one watt of power for cooling.

Many companies have introduced new products to reduce the amount of energy consumed and heat generated by their products. This has been a challenge given that it must accompany their materials changes to accommodate RoHS and other regulatory guidelines.

For example, Western Digital introduced three power saving improvements for its disk drives, with a power reduction of up to 40%. The more efficient use of power indicates that these hard drives will also run cooler.

▲ IntelliPower - By balancing spin speed and transfer rate, as well as by utilizing special caching algorithms, the hard drives reduce energy usage while maintaining "solid performance."

▲ IntelliPark - By unloading the recording heads while the drive is idle, drag is reduced on the disk, requiring less energy to maintain its minimum rotation speed. Also, it disables some of the internal electronics during these rest periods to save additional energy.

Technology to watch includes the Solid-State RAM Disk. With advances in RAM technology, it is now possible to provide the quantity of storage space by using nonvolatile memory instead of a spinning disk platter. This would require less energy to operate, as it has no moving parts. As prices drop, these will be more common in notebook PCs.

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