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We would like to talk a bit more about how hard drives can be more power efficient than many of the Flash SSDs on the market. While a mechanical drive will never be able to reach power requirements as low as shown by the OCZ drive when idling under Windows Vista with drive power management disabled or when playing a DVD stream, there is still a lot of room for improvement.
While many Flash SSDs show idle power requirements that are not clearly below the idle requirement of a hard drive, they will eventually leave mechanical drives in the dust (look at the results of the OCZ drive on the following pages). Until this is the case, the hard drive has a chance to keep up, as Hitachi shows impressively. Typically, 2.5” SATA hard drives require between 0.8 W and 1.5 W when idle, and 2.5 W to 4.0 W peak power.
Many people were wondering why the Hitachi Travelstar 7K200 could do so well in our previous article, although we had measured an idle power that was significantly higher than idle power of some of the Flash SSDs. The reason is simple: idle isn’t always idle. While we’ve been measuring idle power after a few minutes of inactivity, some hard drives will switch into more energy-efficient operating modes a few minutes later. Hence, all the idle power measurements will now be conducted after 10 minutes of inactivity to make sure that a hard drive’s power saving mechanism can come into action. Have a look at the power saving technology as offered by Hitachi:
As you can see , there are various hard drive power states that go all the way from peak power (all on - mode 0) to standby (spin down platters - mode 2) and even off (all off - sleep). While many people will immediately say that the low power we measured must have been measured when the drive is spun down, we can assure you that this isn’t the case. Hitachi implemented a low power idle mode, which will reduce the drive power requirement while still providing sufficient performance to answer requests. Remember this when you check out the test results — especially DVD playback.