MacOS – Toshiba 2TB External Drive Stopped Being Recognised

hard drivehddmacbook promacosusb

After a lot of searching on the internet I have been unable to find a solution to my problem. There are many people having similar problems, but no solution seems to work for me.

I have a 2013 MacBook Pro and I have a Toshiba 2TB External drive which I have used for the past 5 or 6 months to keep copies of my iPhoto Library and my Time Machine backups on. Everything has been fine up until yesterday. I plugged the drive into the USB slot to find it no longer appeared on the desktop. I have tried everything I can think of to get this to work. Here is a rundown of the situation:-

  • I have tried both USB ports on the Macbook.

  • The drive doesn't appear in Disk Utility or System Profiler.

  • I have bought a new USB cable.

  • The drive has it's own power supply and lights up and makes regular noises when on.

  • I have connected it to a PC and managed to access the files using HFSExplorer, which leads me to believe the HDD is okay.

  • I can browse both partitions and extract files to my PC using HFSExplorer.

  • The drive shows up in Disk Manager on Windows and shows the partitions.

  • I have another external drive, my old MacBook HDD in a caddy, which works perfectly, so I don't think its the USB ports either.

This is what I get in Terminal:-

-laeO@ /Volumes
total 24
drwxrwxrwt@  4 root           admin  hidden  136 17 Oct 13:36 .
    com.apple.FinderInfo      32 
 0: group:everyone deny add_file,add_subdirectory,directory_inherit,only_inherit
drwxr-xr-x  32 root           wheel  -      1156 17 Oct 12:18 ..
-rw-r--r--@  1 rebeccaholmes  admin  -      6148  7 Dec  2013 .DS_Store
    com.apple.FinderInfo      32 
lrwxr-xr-x   1 root           admin  -         1 17 Oct 12:54 Macintosh HD -> /

It really is bizarre. I am left thinking my only solution is to go through the arduous process of copying all the files to my windows PC and reformatting the HDD 🙁

Does anyone have a better solution to this problem?

Edit – Since posting I have also tried resetting the MacBook PRAM and SMC. Neither has made any difference.

Edit – Using DiskUtiliy after entering "defaults write com.apple.DiskUtility DUDebugMenuEnabled 1" command lists no external drive.

   "diskutil info disk1s2" returns the message "cannot find disk"

Best Answer

  1. Please quit Disk Utility if it is open and launch Terminal in the folder Applications/Utilities/ with your external drive connected

  2. Enter the following command at the Terminal prompt:

    defaults write com.apple.DiskUtility DUDebugMenuEnabled 1

  3. Press Enter

  4. Quit Terminal
  5. Start Disk Utility and enable 'Show every Partition' in the Debug menu
  6. After a few seconds all partitions should be visible

  7. Mount the partition 'NameOfTheMainPartitionExternalHD' if it is present and greyed out with the blue button Mount. The partition should now be visible on your desktop.

    In the above example the external drive is an SD card and the usually visible partition of the external drive is gDisk. Don't touch disk1s1 (Lion) or EFI (Mavericks)

  8. Please check the format of the partition

  9. If the format is 'Mac OS Extended' you might check the drive for inconsistencies.

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