USB drive not mounting on startup

Discussion in 'OS X Mountain Lion (10.8)' started by rk25123, Jan 17, 2013.

  1. macrumors regular

    Aug 17, 2010
    Hello, I have a WD external hard drive connected directly to my Mac Pro (10.8.2, all updates) via USB, the drive won't mount on startup, and it won't be listed until I unplug it and replug it. The strange thing is that sometimes it does mount normally. I have 2 others WD external drives (different model) which do not present the issue. Any ideas? Thanks for the help!
  2. macrumors newbie

    Jan 15, 2013
    Greece, Athens
  3. macrumors 603


    Bus Powered?
    If so it's a possibility it draws too much power, I think if you open System Profiler you can see the amount of mA it uses under Hardware-USB.
  4. thread starter macrumors regular

    Aug 17, 2010
    The drive is NTFS (so are the other 2)
    That seems to make sense, since the other two drives have their own power supply and this is powered from USB... But then, why does it sometimes mount normally and others I have to unplug and replug it? In System Profiler it says:
    available power: 500 mA
    power required: 500 mA
    So it should work fine...
  5. macrumors 603


    Some drives need an Y-USB cable, I have one and it does not work on a single USB port, it is a Toshiba HD and it sucks a lot of juice from the USB ports, it won't even start on my powered USB 1 amp hub on one USB connector.

    But, long ago I had issues as well with one drive, plug it in, did not work, get it out and in again and it did, this also on one cable.

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