Power Consumption

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. Since this test session focuses on 2.5-inch drives which only consume from a 5V line and compares them with 3.5-inch drives which consume from both 5V and 12V lines, we will be talking about total power consumption. The start-up currents will only be compared for the 2.5-inch models due to the same reason.

The 7200rpm 2.5-inchers are quite modest in terms of the current necessary to start up. Every one of them fits within 1 ampere and should have no problems working in external enclosures powered by two USB ports (of course, you should better install such drives into enclosures with eSATA interface to reveal their full potential, but that’s a topic for a different review). The test is won by the Western Digital Caviar Blue 500GB which is very economical (even in comparison with other 5400rpm drives) but the Seagate Momentus 7200.3 is just a tiny bit worse. The WD Scorpio Black needs a higher current, but again, all of the drives are really good in this test.

The 7200rpm 2.5-inchers consume somewhat more power in idle mode than their 5400rpm mates. The difference is indeed small, only 0.2-0.3W, and even lower with the Hitachi 7K200.

Take note that the 2.5-inch drives are far more economical than the 3.5-inch models. The latter need four times more power and thus generates much more heat. It means that 2.5-inch disks would require less cooling in a densely packed server or compact home PC.

The 7200rpm 2.5-inch drives are not much hungrier than their 5400rpm counterparts at random-address reading and writing. For example, the Seagate Momentus 7200.3 is almost as fast as the WD Scorpio Blue although the latter is among the most economical products in its class. Well, it still does not make it to the level of the latest 5400rpm drives from Seagate (you can view the results of the Seagate Momentus 5400.5 based on two 160GB platters), but that’s the payment for its higher performance. It looks like low power consumption is the priority of modern 2.5-inch drives from Seagate, the inferior speed characteristics being the tradeoff.

The WD Scorpio Black is faster but consumes more. The difference from the Seagate 7200.3 is 0.4W and 0.5W at reading and writing, respectively. This higher power consumption is necessary for the advanced electronics and quick heads, and we guess it is indeed worth the resulting performance benefits.

The 2.5-inch models are not as better than the desktop HDDs as in idle mode: the difference is only twofold now. Anyway, you should remember that larger-capacity 3.5-inch drives will have not one but two or more platters and, accordingly, higher power consumption. And you won’t have much power saving even with 5400rpm 3.5-inchers (but you will have a much higher response time with such models).

The Seagate Momentus 7200.3 delivered higher speeds at sequential operations in our tests and it has high power consumption under such load. It is the most voracious of the tested 2.5-inch drives then, requiring about one third of a watt more than the WD Scorpio Black. The payment for the higher spindle rotation speed is about 0.5W again. The difference between the 2.5-inch and the desktop HDDs is twofold.