MacOS – Booted to Windows how to enable access to a Mac CoreStorage volume


I've installed Windows 8.1 with the Boot Camp Assistant on a solid state drive with a CoreStorage volume. Booted to Windows I can't see the files on my Mac volume anymore.

I'm confused since this is the same setup steps I used to install Boot Camp on an iMac previously and that Windows install has no problems to see the Mac volume and read the Mac files.

How do I regain at least read-only access to my Mac files on the SSD MacBook Pro?

Output of diskutil and gpt:

 -bash-3.2# diskutil list  
 #:                       TYPE NAME                    SIZE       IDENTIFIER  
   0:      GUID_partition_scheme                        *500.3 GB   disk0  
   1:                        EFI EFI                     209.7 MB   disk0s1  
   2:          Apple_CoreStorage                         234.4 GB   disk0s2  
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3  
   4:       Microsoft Basic Data JZ81p64                 265.0 GB   disk0s4  
   #:                       TYPE NAME                    SIZE       IDENTIFIER  
   0:     Apple_partition_scheme                        *1.3 GB     disk1  
   1:        Apple_partition_map                         30.7 KB    disk1s1  
   2:                  Apple_HFS OS X Base System        1.3 GB     disk1s2  
   #:                       TYPE NAME                    SIZE       IDENTIFIER  
   0:                  Apple_HFS JZYsmyt                *234.0 GB   disk2  
                                 Logical Volume on disk0s2  

-bash-3.2# gpt -r -vv show /dev/disk0  
gpt show: /dev/disk0: mediasize=500277790720; sectorsize=512; blocks=977105060  
gpt show: /dev/disk0: PMBR at sector 0  
gpt show: /dev/disk0: Pri GPT at sector 1  
gpt show: /dev/disk0: Sec GPT at sector 977105059  
          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  457756312      2  GPT part - 53746F72-6167-11AA-AA11-00306543ECAC  
  458165952    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC  
  459435488        544           
  459436032  517668864      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7  
  977104896        131           
  977105027         32         Sec GPT table  
  977105059          1         Sec GPT header  

Best Answer

Instead of a default/classical Mac volume like your iMac, your MacBook Pro contains a CoreStorage volume.

Booted to Windows, CoreStorage volumes cannot be mounted and consequently the contained files can't be read - until now.

You would need to revert the CoreStorage volume wrapper that contains HFS+ back to a straight HFS+ volume to regain read-only access.

I'm surprised Apple doesn't have KB article on this, but look here:

Basically, boot to Recovery HD (or another external Mac volume) and then issue the command:

diskutil cs revert E21EC611-3794-4B0D-BFDB-299510FCDFAB

That would take partition 2 on disk0 (the Core Storage part) and revert it to the HFS+ or classic disk layout that Windows knows how to read.