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Not sure what happened. Two days ago I just did a Time Machine backup and today the partition won't mount. The external disk is a WD My Passport bought several years ago and total 2 TB. I partitioned it into two partitions, 1TB each. One partition for Time Machine and one for general backup. Both are formatted as OSX Extended Journal. Usually when I plug in the drive both partitions will mount, but today only the Backup partition mounts. If I try to Eject the Backup partition the disk is greyed out and it seems the system is trying to eject it forever and ever. When I open Disk Utility it just keeps loading and loading and loading, see screenshot. I have Restarted many times, unplugged and plugged both ends of the USB cable, no luck yet.

enter image description here

Strangely enough when I plug in the drive onto my Bootcamp Windows 10 both partitions mount just fine and I can read files on both. So seems like the drive itself works fine, just OSX is refusing to mount it. Can anyone help figure out what to do here? Thank you very much.

Edit: Output of "diskutil list":

diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            449.0 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data BOOTCAMP                50.4 GB    disk0s4
/dev/disk1 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS Time Machine WD         1000.0 GB  disk1s2
   3:                  Apple_HFS Backups WD              999.9 GB   disk1s3


diskutil info disk1s2
   Device Identifier:        disk1s2
   Device Node:              /dev/disk1s2
   Whole:                    No
   Part of Whole:            disk1
   Device / Media Name:      Time Machine WD

   Volume Name:              Time Machine WD

   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
   Volume UUID:              46CE8ED4-2859-3F76-AEAD-6CBB7CC0CD02
   Disk / Partition UUID:    D6FBBEEE-E4CA-4C31-824A-B4F0EAC26AB9

   Total Size:               1000.0 GB (1000000000000 Bytes) (exactly 1953125000 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


sudo fdisk /dev/disk1
Password:
Disk: /dev/disk1    geometry: 243197/255/63 [3906963456 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 - 3906963455] <Unknown ID>
 2: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 3: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
Kevins-MBP:~ kevinpw$ sudo gpt -r show /dev/disk1
       start        size  index  contents
           0           1         PMBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34           6         
          40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
      409640  1953125000      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  1953534640      262144         
  1953796784  1952904488      3  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  3906701272      262151         
  3906963423          32         Sec GPT table
  3906963455           1         Sec GPT header
Kevins-MBP:~ kevinpw$ diskutil verifyvolume /dev/disk1s2
Started file system verification on disk1s2 Time Machine WD
Verifying file system
File system check exit code is 8
Error: -69845: File system verify or repair failed
Underlying error: 8: POSIX reports: Exec format error

Edit: New verify results after disk mysteriously mounts itself:

diskutil verifyvolume /dev/disk1s2
Started file system verification on disk1s2 Time Machine WD
Verifying file system
Using live mode
Checking extents overflow file
Checking multi-linked files
Checking catalog hierarchy
Checking extended attributes file
Checking volume bitmap
The volume Time Machine WD appears to be OK
File system check exit code is 0
Finished file system verification on disk1s2 Time Machine WD
  • 1
    You can start by posting the output from the Terminal application command diskutil list. – David Anderson May 14 '16 at 7:42
  • Thanks @DavidAnderson. I have posted it as you requested. Looks like the Time Machine partition can be seen from this command. – rabbid May 14 '16 at 8:23
  • 1
    Ok, post a dump of the drives's partition tables. The commands are sudo fdisk /dev/disk1 and sudo gpt -r show /dev/disk1. These commands will not change your computer. Some commands may ask for your login password. This is normal. If everything looks Ok, then I will have you run a command to verify the filesystem of the partition that will not mount. (i.e. diskutil verifyvolume /dev/disk1s2) – David Anderson May 14 '16 at 8:58
  • Thanks again @DavidAnderson. I've posted everything you asked for, but the verifyvolume failed. – rabbid May 14 '16 at 9:11
  • 1
    You can run the command to repair the volume but I doubt it will do any good. The command is diskutil repairvolume /dev/disk1s2. If repair fails, I am out of ideas. Either erase the partition or wait for someone else to post an answer. – David Anderson May 14 '16 at 9:26

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