Forum Thread

How much wattage does hard drive draw?

eli2k 1,056 199 May 19, 2009 at 09:18 PM
I used one of the PSU calculators online, and it figured out one hard drive draws 30watts! Can someone let me know how much a hard drive really draws (typical 7200rpm hard drive, Seagate/WD, 500gb-1000gb) when it's working and not just idling?

Thanks,
- Eli
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#2
Watts = Volts * Amps. Now, obviously, it depends on the HDD. For instance, an old 40GB HDD I Have says that the 12VDC line uses 0.35A and the 5V line uses 0.63A. So, 12*.35 + 5*.63 = 7.35W.

This 1TB HDD [zdnet.com] uses 12 * .55 + 5 * .7 = 10.1W.

30W seems excessive unless you're talking ultra fast SCSI.
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Last edited by kakomu May 19, 2009 at 09:33 PM
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#3
Thanks, kakomu. Look at this http://extreme.outervision.com/PSUEngine

I wanted to build a mini-ITX Atom platform, with just one stick of RAM, and 2-3 hard drives, and every hard drive I hadd puts on quite a bit of wattage. Guess I'll just calculate it myself, then.
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#4
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#5
You need another power calculator. Wink

Here [xbitlabs.com] is what Xbit Labs measured for several 1TB 3.5" HDs under many different conditions. Summary: about 3-8W while just spinning at idle, twice that during random reads, 18-38W for the first few seconds after turn-on. I believe that each 3.5" platter needs about 1/2W because of wind resistance. Continuous operation at an average of 5W for a 3.5" HD means it barely gets warm when ventilated (even convection alone, no fan needed), 7-8W means pretty hot but still OK. Green 3.5" HDs should stay pretty cool even in a poorly ventilated external enclosure.
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#6
Hmm, that's really interesting. So for planning a PSU, I have to take into account t his huge start-up current, which shoots up really high...unless I let the PSU be overloaded a bit during start-up for a few seconds.
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#7
Quote from eli2k View Post :
Hmm, that's really interesting. So for planning a PSU, I have to take into account t his huge start-up current, which shoots up really high...unless I let the PSU be overloaded a bit during start-up for a few seconds.
It's actually not that much current, so don't worry about it.
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#8
Quote from eli2k View Post :
I wanted to build a mini-ITX Atom platform, with just one stick of RAM, and 2-3 hard drives
Most MITX motherboards only have two SATA headers.
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#9
Quote from DBC View Post :
Most MITX motherboards only have two SATA headers.
I'm planning to use a mini-ITX Atom-based system with an 80w PSU, which is why I want to be careful.
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#10
EDIT: Seems they run about 25W spin up, 8-12W idle; obviously varies by manuf
but...
Think about this, a USB is 2.5W and can run a 5400RPM drive, why does a 7200rpm drive require so much more?
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Last edited by typerazor May 20, 2009 at 07:36 PM
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#11
Well, based on the link http://www.xbitlabs.com/articles/...html#sect0 larrymoencurly if you calculate the number of watts that is being drawn by the current that the measured, it gets pretty high.
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#12
Quote from eli2k View Post :
Well, based on the link http://www.xbitlabs.com/articles/...html#sect0 larrymoencurly if you calculate the number of watts that is being drawn by the current that the measured, it gets pretty high.
2.83A*12V + .83A*5V = 38.11W, and that's only for a few seconds:

+12V amp draw during spin-up (StorageReview.com):

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#13
Quote from typerazor View Post :
EDIT: Seems they run about 25W spin up, 8-12W idle; obviously varies by manuf
but...
Think about this, a USB is 2.5W and can run a 5400RPM drive, why does a 7200rpm drive require so much more?
huh? The USB runs Laptop drives. 2.5" small drives that need less power.
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