I have several Ext. HDD attached via USB to my iMac. Turning the mac on this morning three of the four drives mount no problem. (all in the same ext power / usb tower) but one drive does not mount.

I went into Disk Utility and the drive shows up there but it's child shows up greyed out. When I select the child it shows that I can mount it but when I actually hit the mount button nothing else happens. The button does not show unmount but stays as mount. enter image description here

It shows the child as being all yellow (other) but its far from full.

Can anyone help ?

Many thanks all

Is this what you need ? If not let me know, thanks for your help.

enter image description here

Device Identifier:        disk3s2
   Device Node:              /dev/disk3s2
   Whole:                    No
   Part of Whole:            disk3
   Device / Media Name:      E Drive

   Volume Name:              

   Mounted:                  No

   File System Personality:  HFS+
   Type (Bundle):            hfs
   Name (User Visible):      Mac OS Extended
   Journal:                  Unknown (not mounted)
   Owners:                   Disabled

   Partition Type:           Apple_HFS
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 USB
   SMART Status:             Not Supported
   Disk / Partition UUID:    BB43A59F-CA7A-407B-A912-89CA19F5C00C

   Total Size:               999.9 GB (999860912128 Bytes) (exactly 1952853344 512-Byte-Units)
   Volume Free Space:        0 B (0 Bytes) (exactly 0 512-Byte-Units)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (not mounted)

   Device Location:          External
   Removable Media:          No

Like that ?

It didn't mount :o(

Last login: Thu Apr  7 08:40:46 on ttys000
Pauls-iMac:~ pual$ diskutil mountDisk /dev/disk3
One or more volume(s) failed to mount
Pauls-iMac:~ pual$ 
  • Could you please post the information of diskutil list and diskutil info /dev/diskxsz where diskxsz is the disk device identifier (left column lowest field in DU) of said partition Untitled to your question? – perhapsmaybeharry Apr 6 '16 at 16:43
  • Not sure if this is what you are asking if not let me know. Thanks for your reply. – paulcrouch Apr 6 '16 at 20:53
  • try diskutil info /dev/disk3s2 instead. Also, you can format the terminal output as code by indenting plain text four spaces or selecting all code and clicking the {} button. – perhapsmaybeharry Apr 7 '16 at 1:26
  • @perhapsmaybeharry is that helpful ? – paulcrouch Apr 7 '16 at 7:48
  • 1
    Pretty much the same issue. Were you able to find a solution to this? – Chintan Parekh Nov 23 '16 at 7:56

In my experience, this is a clear cut hardware issue. If you cannot mount the volume, even after trying to do so forcibly, it’s almost always due to physical failure of the hard drive disk.

You can test with varied USB connections (different cable, then different hub) to eliminate the alternatives and confirm the diagnosis. Best of luck.

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