You can refer to our article called Hard Disk Drive Power Consumption Measurements: X-bit’s Methodology Indepth for details on this test. We’ll just list the specific modes we measure the power consumption in:
- Start (the current the drive consumes when speeding up its spindle)
- Idle (the drive is not accessed at all, but it is turned on and ready to work)
- Random Read and Write
- Sequential Read and Write
Let’s check out each mode one by one.
You might have supposed that Hitachi’s model would have the highest power requirements due to its three-platter design. However, it is the Western Digital that has the highest startup current. It probably needs such a high current to spin up its spindle and get ready to work faster.
Well, the time the HDD takes to spin up is unimportant for mobile storage devices whereas the maximum current is a factor that must be taken into account. As we know, the USB interface provides a current of 0.5A per connector. Many modern mainboards provide even more, but there is a limit anyway. Many users already had this problem when their USB drive just would not start up because of the lack of current for that. This problem was solved by using a power cord that could be plugged into two USB ports but this only gives you 1 ampere while Western Digital has stepped beyond that point. Will we see USB power cords with three connectors now?
The Toshiba has low power consumption in idle mode, and the other drives have similar results. Take note that the Hitachi needs a little bit more power than the others: its motor has to rotate three instead of two platters!
The drives needs about the same amount of power to do random reading. Well, this should have been expected since their platters are rotating, their heads are moving about, but their electronics is idle – all under similar conditions. The drives from Hitachi and Western Digital save less power at writing than their opponents as they perform deferred writing. The more advanced electronics of those HDDs just needs somewhat more power to do its job.
Here, not only deferred writing but also look-ahead reading is at work. Therefore the drives have about the same power draw in both modes. It is clear once again that the excellent speed of the Western Digital is accompanied with high power consumption. This extra half of a watt may be a problem for a mobile storage device. To remind you, the maximum current of 0.5A across a 5V bus equals 2.5 watts, which is lower than the 3 watts required by this HDD. And you should also take the consumption of the USB-SATA bridge into account.