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How can I recover a FAT partition originally created under OS X and used mainly from Bootcamp Windows which now looks as follows:

  • OS X diskutility shows it in grey, as unmounted partition disk0s4 (despite a user-friendly name I given); attempt to mount it doesn't change anything. Capacity is shown correctly, but no Available/Used/Number of files is shown
  • Windows 7: Computer > Manage > Disk Management shows the partition in the list (as RAW, Healthy, Primary), but again no capacity/used/free space is shown
  • Windows Explorer reports:

    "X:\ is not accessible. The volume does not contain a recognized file system. Please make sure that all required file system drivers are loaded and that the volume is not corrupted".

Is there a "completely software" way to recover that partition (like re-creating MBR in some smarter way that I'm trying to do)--rather than to proceed to manually restoring file-by-file with some advanced dead-HDD recovery solutions?


As a background for the problem:

  • I originally created the following set of partitions under OS MtLion X:
    1. bootable OS X MtLion
    2. bootable Yosemite
    3. Bootcamp (Windows 7)
    4. shared FAT32 data partition
  • after(?) installing Windows on Bootcamp partition, I manually created MBR with the following subset of partitios to be visible under Windows: Bootcamp, Shared, MtLion. I used gdisk from gptfdisk (as detailed in this post).
  • for several months I worked primarily under Windows, using Shared heavily
  • recently I updated some piece of software under MtLion OS X (or Yosemite?) which(?) led to the above problem. I used to believe the update didn't deal with recovery partitions, but I may be wrong

Previously, every time OS X update created/updated recovery partition (and some of Windows partitions became inaccessible), simply re-creating MBR with the same original set of partitions helped every time. But it doesn't any more.

It's SSD installed to 13" MBP late 2010.


Per David Anderson's clarification, here are several logs:

$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *480.1 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:                  Apple_HFS SSD MtLion              100.0 GB   disk0s2
   3:                 Apple_Boot Recovery SSD MtLion     650.0 MB   disk0s3
   4:       Microsoft Basic Data                         259.4 GB   disk0s4
   5:                  Apple_HFS SSD Yosemite            29.2 GB    disk0s5
   6:                 Apple_Boot Recovery HD             650.0 MB   disk0s6
   7:       Microsoft Basic Data BOOTCAMP SSD            90.0 GB    disk0s7
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk1
   1:                        EFI                         209.7 MB   disk1s1
   2:                  Apple_HFS HDD MtLion              100.0 GB   disk1s2
   3:       Microsoft Basic Data BOOTCAMP HDD            65.0 GB    disk1s3

Here in diskutil output, disk1 is HDD which currently serves as data-only; no problems with it--I just kept the output intact.


$ sudo gpt -r show /dev/disk0
Password:
gpt show: /dev/disk0: Suspicious MBR at sector 0
      start       size  index  contents
          0          1         MBR
          1          1         Pri GPT header
          2         32         Pri GPT table
         34          6         
         40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
     409640  195312496      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  195722136    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  196991672       1352         
  196993024  506595328      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  703588352       1832         
  703590184   57063864      5  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  760654048    1269536      6  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  761923584  175777792      7  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  937701376       1679         
  937703055         32         Sec GPT table
  937703087          1         Sec GPT header

$ sudo fdisk /dev/disk0
Disk: /dev/disk0    geometry: 58369/255/63 [937703088 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE    0   0   2 -   25 127  14 [         1 -     409639] <Unknown ID>
 2: 07 1023 254  63 - 1023 254  63 [ 196993024 -  506595328] HPFS/QNX/AUX
*3: 07 1023 254  63 - 1023 254  63 [ 761923584 -  175777792] HPFS/QNX/AUX
 4: AF   25 127  15 - 1023 254  63 [    409640 -  195312496] HFS+        
  • Post to your question the output from the commands diskutil list, sudo gpt -r show /dev/disk0 and sudo fdisk /dev/disk0. None of the commands will change your computer. Your login password many be asked, this is normal. – David Anderson Sep 7 '15 at 12:46
  • If you had installed your Windows partitions before your OS X partitions, then these types of problems would not occur. – David Anderson Sep 7 '15 at 12:51
  • @DavidAnderson : I just added all the outputs, please let me know if I can provide any more info. – yurkennis Sep 7 '15 at 20:22
  • @DavidAnderson Sorry to bring up this, but do the output show some chances for recovery? – yurkennis Sep 9 '15 at 23:46
  • I do not see any error in the MBR partition table or GPT that would cause a FAT formatted partition to not mount. So, I do not know of a way to recover your files. – David Anderson Sep 10 '15 at 4:04

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