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I have 2 external USB hard drives which are always connected to my laptop. The reasons are mixed; I need them so often and I'm too lazy to plug/unplug them again and again.

However I'm concerned about the laptop power they consume when I'm not using them so I was wondering if I could add a physical on/off switch to the USB cables that connect them.

So would it be harmful to the laptop/Hard drive if I were to install a physical on/off switch on the red cable of USB connector and I turn it off? I would do this after clicking Safely remove the Device from Windows.

I believe this would cut the power of the USB device connected. I just need to be sure of the risks as the remaining 3 cables would still remain connected.

On the other hand, if you think this is completely inadvisable idea you can suggest another approach to achieving the same goal?

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  • Why not just send the drives the command to spin down? That will negate most of the power usage. (The electronics will stay on, but typically those do not consume much power compared to what is needed to keep a platter running).
    – Hennes
    Oct 5, 2014 at 18:21
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  • You may want to go into Device Manager and set "Optimize for quick removal". Oct 6, 2014 at 3:15

3 Answers 3

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If you are confident in your splicing and wiring capabilities, go for it. Remember to safely eject the external hard drive before turning off the switch.

I found instructions on how to set up a USB power switch here, although the instructions are for a USB header on a motherboard.

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Watch what happens when you click "safely remove". (And maybe try "eject" as well; I know they at least do slightly different things). I suspect you'll see the drives spin down anyway. Spinning down the drive will avoid most of the power draw.

Then you just need a way to re-enable it!

Disabling and re-enabling in Device Manager should work. You can script that using devcon.exe. I expect you can find a persistent identifier for the device (preferably not the usb port #, or it'll break when you do start re-arranging things), and put it in a batch file.

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As far as external hard-drives, the only real risk is interrupting an operation. At worst it could mean that a large file only gets partially written and therefore lies corrupt (imagine losing weeks worth of work if you broke an important document). Filesystem information could also get wonky if the interrupt is in the middle of a change there too.

You can ensure this won't be an issue by first ejecting the drive. When you eject the drive, it makes the drive no longer available to the filesystem, but it will still finish up any reads/writes that it was issued before the eject (so it won't kill your files).

Because these are portable drives, I also want to mention that mechanical drives can risk physical damage. Some hard-drives have a mechanism which automatically pull back the reading apartus within the hard drive, but not all of them do. It could risk physical damage to the drive if it was moved around while these are out. Many a laptop drive has gone bad due to falling (though many laptop drives these days have a built-in measure that detects falling to protect the drive).

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  • Thanks for explaining that all. I'll surely eject it first. Thanks
    – d-coder
    Oct 6, 2014 at 23:38

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