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I use an external HDD on a machine. Lately, the hdd has been dropping the USB connection (Windows plays the disconnect/reconnect sounds, then the hdd device goes away for half a second, and comes back).

At first I blamed the HDD (it's new, "Western Digital" if that means anything to you (they all fail eventually)). Suddenly one day the HDD completely disappeared from the machine (it wouldn't show up).

Naturally I panicked and am now mirroring that hdd's data on another hdd, using another machine.

Funny thing is, the hdd in question works fine on this other machine. it doesn't seem to be having any issues.

How can I diagnose if there is a problem or not with the USB ports in my machine? It has 8 of them and I can't remember which one the hdd was plugged into when it was failing --=

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All I can suggest is to use the drive on all the ports, determine if it is just one or all the ports misbehaving – Moab Sep 6 '12 at 15:53

External drives that are USB-powered can, at peak-usage, require more current than a USB port can deliver. The current available on a USB port may depend on the machine or how many other USB devices are attached to the same internal USB hub.

  • If the drive supports it (most do) plug in an external PSU to see if the problem persists.
  • If not, plug it into a POWERED USB-hub

Wikipedia says

Some devices, such as high-speed external disk drives, require more than 500 mA of current[42] and therefore may have power issues if powered from just one USB 2.0 port: erratic function, failure to function, or overloading/damaging the port. Such devices may come with an external power source or a Y-shaped cable that has two USB connectors (one for power+data, the other for power only) to be plugged into a computer. With such a cable, a device can draw power from two USB ports simultaneously.[43]

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Interesting, but it is externally powered HDD – bobobobo Sep 6 '12 at 18:02
@bobobobo: yes but is the external wall-wart lying on the floor? Are you sure the DC cable doesn't have a break where your friend trod on it (the internal conductors can break without the external plastic sheath looking damaged). I have an external HDD that can be externally powered but draws power from USB when the power supply isn't plugged in at the wall. P.S. Don't forget to update your Q with additional/missing details like this. – RedGrittyBrick Sep 6 '12 at 19:59

In order to troubleshoot the problem you will have put in some time and effort.

The problem could be USB a port on the PC, the USB connector on the PC or drive bay, or even the cable itself.

Its most likely not the USB cable or port on the drive, if you are using the same cable on the other machine. As for the USB port on your PC, it wont take you long to test them all.

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The dropping issue happens only about once every half hour or so -- so testing in that way is kind of inefficient -- you have to be watching closely the computer to actually see it drop/reconnect, if the sounds off you won't hear it happen. I'm looking for another way. – bobobobo Sep 6 '12 at 18:03

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