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Power Consumption

You can refer to our Hard Disk Drive Power Consumption Measurements: X-bit’s Methodology in Depth for details on this test. We will just list the specific modes we measure the power consumption in:

  • Start (the electric current the HDD consumes when starting up)
  • Idle (the HDD 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.

The WD is the most economical HDD when starting up. It expectedly needs less power than the others from the 12V line which powers an HDD’s mechanics. It takes more time to spin up, without having high peaks of power consumption, and has fewer platters with heads. You should note that the peak power draw of these HDDs is up to 12 amperes on the +12V line when they are starting up. This makes it clear why the SATA standard introduced the staggered spin-up feature. If ten such HDDs were starting up simultaneously, they would require up to 20 amperes from the +12V line, which is quite a lot.

The WD makes up for its losses in the earlier tests by being the most economical product in idle mode. It needs only half the power required by the Hitachi and Seagate. Well, it has one platter less and its platters are rotating at 5400 RPM, after all. The 5-platter 7200RPM models are good enough, too. We can also note that the Hitachi needs half a watt less than the Seagate.

According to our methodology, we measure the power consumption 10 minutes after we stop all disk requests. But when we left our HDDs on the testbed for a longer time, we saw very interesting numbers:

Yes, every HDD is consuming from the 5V line only, and a very modest amount of power at that. What does it mean? It means that they have parked their heads and turned off the spindles. They have switched into a deep sleep mode. The numbers you can see in the diagram are the power consumption of the electronics waiting for a command to wake up. Each of the three HDDs falls asleep after 20 minutes of being idle. So, don’t worry if you can’t hear a connected HDD. It may be just sleeping and saving power when there is no work for it to do.

The energy-efficient drive from WD is still in the lead at random-address loads, but its advantage isn’t very large at random reading where an HDD has to move its heads about very quickly. The Hitachi is somewhat better than the Seagate at random reading: this must be the tradeoff for the Seagate’s excellent read response time. The two 7200RPM models need about the same amount of power for random writing where deferred writing algorithms come into play and reduce the load on the HDD’s mechanics.

The WD is the most economical HDD at sequential reading and writing, too. However, it doesn’t have the advantage it enjoyed at random-address operations or in idle mode. The Hitachi is somewhat more economical than the Seagate, probably because its electronics has lower power consumption. We must acknowledge the dramatic progress of Hitachi products, by the way. The company’s 5-platter HDDs of the previous generation consumed about 50% more power!

 
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