Continuous Power vs. Peak Power at Spin-Up

Most of the power used by a modern hard disk drive is taken up by the spindle motor. Due to their smaller, more efficient designs, newer drives require relatively little power to keep their platters spinning continuously. Even drives with faster spindle speeds take less power than the large, inefficient motors of the drives of a decade ago. However, when the hard disk is first started up, the motor can draw a peak level of power that is more than two times what it takes to keep the disks spinning. (Most things require more energy to start them in motion than to keep them in motion, but in the case of hard disk motors this is especially so because of their electrical characteristics.) While in most cases even the peak start-up power usage isn't all that much, there can be an issue when you are using multiple hard disks that all try to spin up at once when you turn on the machine. The ratings of your power supply, particularly for the +12 V level, must be sufficient to take this initial demand into account.