tissuebox

Q: Why does my external USB drive randomly disappears, unmounts, ejects itself

Hello,

I've seen this problem posted under different headlines but I thought I'll post it here under a clearer headline, and hopefully, a better description.

 

When plugging a brand new external USB drive into my MacBook Air (formatted and prepared by Apple's Disk Utility), OSX seems to unexpectedly unmount it a few minutes later. I've been having this issue with an older external drive, I thought there was something wrong with the drive itself so I bought a new external USB drive (different brand) and copied all the data over (TimeMachine files), but surprisingly the problem presisted.

 

As I mentioned, I use the external drive for my TimeMachine, and every few minutes or so, the drive disappears from the desktop and an error pops up saying:

 

"The disk was not ejected properly. If

possible, always eject a disk before

unplugging it or turning it off.

To eject a disk, select it in the Finder and choose File

> Eject. The next time you connect the disk, Mac OS

X will attempt to repair any damage to the

information on the disk."

 

The only way to mount it again is to turn the drive off an on again. Unpluging the USB cable for a couple of minutes then plug it back again won't do. It even becomes unavailable in Disk Utility (when pluggen in of course).

 

I tried plugging the USB drive directly into my MacBook Air, into my Thunderbolt display through USB, and into my external USB hub. All with the exact same symptoms.

 

NOTE: Although this problem seems to be common on OSX, I'm not sure, if in my case, it's related to the fact that I use the software PKard, which allows OSX to accept Government CAC cards (otherwise known as SmartCards).

 

Computer: MacBook Air 13-inch, Mid 2011

OS: Mac OS X 10.8.4 (12E55)

Memory: 4 GB DDR3

External Display: 27" Thunderbolt display

Eternal USB devices: SCR331 Card Reader; USB SATA drive enclosure (plugged into display); 4-port USB hub.

MacBook Air, OS X Mountain Lion (10.8.4)

Posted on Jul 3, 2013 10:36 AM

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Q: Why does my external USB drive randomly disappears, unmounts, ejects itself

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  • Helpful answers

  • by Linc Davis,

    Linc Davis Linc Davis Jul 3, 2013 10:48 AM in response to tissuebox
    Level 10 (207,983 points)
    Applications
    Jul 3, 2013 10:48 AM in response to tissuebox

    If the drive is bus-powered, it may be drawing more power than the bus can supply. Connect the AC adapter, or connect the drive to a powered hub.

     

    To rule out third-party software as the cause of the problem, do as follows.

     

    Please read this whole message before doing anything.

    This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

    The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, or by a peripheral device.

     

    Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards. Boot in safe mode and log in to the account with the problem. Note: If FileVault is enabled, or if a firmware password is set, or if the boot volume is a software RAID, you can’t do this. Ask for further instructions.
       
    Safe mode is much slower to boot and run than normal, and some things won’t work at all, including sound output andWi-Fi on certain iMacs. The next normal boot may also be somewhat slow.

    The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

     

    Test while in safe mode. Same problem?

     

    After testing, reboot as usual (i.e., not in safe mode) and verify that you still have the problem. Post the results of the test.

  • by Timbrely Pearsley,

    Timbrely Pearsley Timbrely Pearsley Oct 19, 2015 9:38 PM in response to tissuebox
    Level 1 (5 points)
    Oct 19, 2015 9:38 PM in response to tissuebox

    I'll just put this here, in case it helps anyone… verify that the USB cable is not the problem.