MacOS – Shared data partition for Bootcamp no longer accessible

bootcampmacospartitionwindows

I have my Macbook Pro running Mountain Lion setup with partitions as follows:
disk0s1 (unnamed) – EFI partition
disk0s2 ("Macintosh HD") – OSX partition
disk0s3 ("Recovery HD") – OSX recovery partition
disk0s4 ("BOOTCAMP") – Windows 7 partition created through Bootcamp
disk0s5 (currently unnamed, but should be "Data") – exFAT partition to be shared between OSX and Windows.

Up until yesterday everything was working fine, but now the Data partition is no longer accessible by OSX or Windows. OSX simply won't mount the partition and Windows claims the disk needs to be formatted. I believe this is due to a corrupt partition table and could use some help in figuring out how to resolve this.

Unfortunately, I can't remember exactly how I created the various partitions. I would have thought I created the Bootcamp partition through the usual means and then shrunk the OSX partition to make room for the new partition, but the layout mentioned above seems to suggest otherwise. I may have created a large Bootcamp partition and then manually shrunk that to make room for the Data partition. Either way, I created a hybrid MBR partition using GPT fdisk.

Somewhat ironically, I think this debacle was caused by something I did while troubleshooting an external hard drive that is no longer readable (hardware failure). In the course of troubleshooting the external drive I had used fdisk and the Disk Management utility in Windows 7, but shouldn't have done anything to my main drive. I'm not sure, however, if just using these utilities attempts to "correct" and issues it deems necessary.

At first I thought that maybe the MBR table got corrupt so I recreated it using gdisk. This solved nothing. I had dumped out the table before and after using fdisk -d and the results were identical. After more thought, I realized that OSX probably wouldn't be using the MBR anyway, so now I'm stumped.

I've tried googling for some clues, but most of the results I've found are about the Windows partition no longer working and usually it's because of a corrupt MBR.

Any thoughts on the next steps to take would be greatly appreciated.

Best Answer

After a lot of trial and error and research I came across this post that solved my issue: https://discussions.apple.com/message/19084645#19084645

Long story short, running fsck_exfat on the Data partition (disk0s5) indicated that the main boot region needed to be updated and it provided an option to update it. Sure enough, this fixed it.

Prior to running fsck_exfat I tried the Verify Disk option on the partition in Disk Utility and it almost immediately failed saying "Invalid sector size: 0". Clicking the Repair Disk option failed and said the disk needed to be reformatted.

After running fsck_exfat and updating the main boot region Disk Utility still showed the partition as "disk0s5" rather than "Data". Clicking the Verify Disk option still gave there error saying the sector size was invalid, but the the partition name suddenly changed to "Data". Then, clicking Verify Disk again said everything was fine.

Hopefully this will help someone else out there. Or me, the next time I run into this...

Related Solutions

Windows – how to expand bootcamp boot partition to previously existed NTFS data partition

To share with other users facing a similar situation, here is how I solved the problem--and avoided completely reinstalling OS X and Windows. For reference, my OS X version was Mountain Lion when I started solving the problem--and I needed to upgrade to Mavericks in the end.

Back up Windows partition with WinClone to an external HDD
Run "Backup now" in Time Machine to make sure I have a latest backup of OS X partition
Under OS X Disk Utility, remove Windows system partition (which is typically labeled BOOTCAMP)
In OS X Recovery boot, remove OS X partition and create it from the scratch (make it use whole HDD space)
Install a clean OS X (my MBA 2011 allowed only Lion--if I remember correctly, it's fine as long as it's not a later release than my Time Machine backup)
Restore my OS X partition from Time Machine. It makes Recovery Partition disappear, we'll fix it in the next step
From AppStore, reinstall Mountain Lion. It's only needed to re-create the Recovery Partition.
Under OS X Disk Utility, manually create a FAT partition for Bootcamp following WinClone support article. WinClone will convert it into NTFS in the next step.
This is where you decide how HDD space will be split between OS X and Windows.
Restore Bootcamp partition from your backup (#1) to the Windows partition you created in #8.
Boot Windows under Bootcamp; it can run CHKDSK automatically, reporting that volume could be dirty--but didn't find any problems.
If you use Trackpad++, it needs to be reinstalled now. Boot Windows under Bootcamp, reinstall PowerPlan Assistant first, then Trackpad++.
Under OS X, re-create virtual machine in Parallels.
Upgrade to Mavericks.
Move to Bootcamp system partition all the data files that were originally stored on Windows data partition (provided you have their backup).

The only problem that's left at this point is that Parallels freezes VM when used in "all apps in one window" default mode (which is not Coherence, Fullscreen or Modality mode). Will seek solution for it later; at least it is stable for a week now in Coherence mode.

Before following the above sequence, I tried to recreate data partitition with Windows, converting the unallocated space that sized exactly like the lost partition. Failed: I found that there is a new partition which originally wasn't there: sized 620MB, but it didn't appear as recovery partition among Startup Disks on boot. Didn't try deleting it though, maybe it could help.

MacOS – Bootcamp: ‘No Bootable Device error’ after resizing partition El Capitan

Sorry about my English. I mean I've made the Macintosh HD partition 10 GB smaller so I later could make in Windows the Bootcamp partition bigger. When I made the Macintosh partition smaller, Disk Utility made a new unnamed partition of that 10 GB. This means there were a total of 5 partitions. In Terminal the BOOTCAMP partition was situated on number 5 and the unnamed new empty partition on number 4. I think the problem is that the system only can boot the first 4 partitions. I've deleted the new empty partition again and set the Macintosh HD at its original size, so BOOTCAMP is now again on #4;

MBP-van-Daniel:~ daniel$ sudo diskutil list
Password:
/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            418.4 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data BOOTCAMP                81.0 GB    disk0s4
/dev/disk1 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *1.0 TB     disk1
   1:               Windows_NTFS My Passport             1.0 TB     disk1s1
/dev/disk2 (disk image):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     Apple_partition_scheme                        +10.5 MB    disk2
   1:        Apple_partition_map                         32.3 KB    disk2s1
   2:                  Apple_HFS Remote Desktop Conne... 10.3 MB    disk2s2

In my first post I had deleted the 10 GB empty partition already. I've installed Refind and after using the reinit and write command I'm now able to choose every time I start up my macbook, several options to boot like Macintosh, Windows and other devices. Now I can boot again into Windows. The only problem is that if I make Macintosh HD partition smaller, a new partition is created that comes at #4 so that BOOTCAMP moves to #5.

Answering klanomath's question brings this;

MBP-van-Daniel:~ daniel$ sudo fdisk /dev/disk0
Password:
Disk: /dev/disk0    geometry: 60821/255/63 [977105060 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 -     409639] <Unknown ID>
 2: AF 1023 254  63 - 1023 254  63 [    409640 -  817223864] HFS+        
 3: AB 1023 254  63 - 1023 254  63 [ 817633504 -    1269536] Darwin Boot 
*4: 0C 1023 254  63 - 1023 254  63 [ 818903040 -  158201856] Win95 FAT32L

and;

MBP-van-Daniel:~ daniel$ 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  817223864      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  817633504    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  818903040  158201856      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  977104896        131         
  977105027         32         Sec GPT table
  977105059          1         Sec GPT header

Best Answer

Related Solutions

Windows – how to expand bootcamp boot partition to previously existed NTFS data partition

MacOS – Bootcamp: ‘No Bootable Device error’ after resizing partition El Capitan

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