alekseyfromsan francisco

Q: Mac OS recognizes NTFS as ExFAT

I have an external 2Tb HD with two partitions one for Time Machine and another for Windows, formatted as NTFS. However my MacBook  recognizes the latter as ExFAT, shows only "System Volume Information" and "$RECYCLE.BIN", but not other files I wrote in Windows, and allows writing on the partition as ExFAT! At the same time when I boot in Windows 10, it shows the partition as NTFS and does not show system files (".Spotlight-V100", ".Trashes", and ".fseventsd"), written by Mac OS. This looks weird and I think Mac OS damages my data on NTFS partition.

 

I have the latest version of El Capitan 10.11.3 and Windows 10.

MacBook Pro with Retina display, OS X El Capitan (10.11.2), Windows 10 in BOOTCAMP

Posted on Feb 11, 2016 5:26 PM

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Q: Mac OS recognizes NTFS as ExFAT

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  • by alekseyfromsan francisco,

    alekseyfromsan francisco alekseyfromsan francisco Feb 12, 2016 4:49 PM in response to Drew Reece
    Level 1 (8 points)
    Notebooks
    Feb 12, 2016 4:49 PM in response to Drew Reece

     

    Windows will not write it's changes to the partition table that the Mac created (GPT/GUID). Windows will use it's own partition table instead (MBR). That will be 'out of sync' with the original GUID partition table. It is valid to have two partition tables (read up on 'hybrid MBR/GUID') but keeping them in sync is not automatic because it can break other installed OS's.

    Could you tell me what do you see on this picture? Does it say MBR or GUID (GPT)?

    props.png

  • by Drew Reece,

    Drew Reece Drew Reece Feb 14, 2016 7:54 AM in response to alekseyfromsan francisco
    Level 5 (7,619 points)
    Notebooks
    Feb 14, 2016 7:54 AM in response to alekseyfromsan francisco

    alekseyfromsan francisco wrote:

     

     

    Windows will not write it's changes to the partition table that the Mac created (GPT/GUID). Windows will use it's own partition table instead (MBR). That will be 'out of sync' with the original GUID partition table. It is valid to have two partition tables (read up on 'hybrid MBR/GUID') but keeping them in sync is not automatic because it can break other installed OS's.

    Could you tell me what do you see on this picture? Does it say MBR or GUID (GPT)?

    props.png

     

    Yes it's GPT/GUID – the default scheme on OS X where you formatted this disk, is this meant to be shocking to us?

     

    Use can use another disk tool and you may see the protective MBR that all GPT disks have. I don't know how accurate that Windows tool it is, it may not show hybrid MBR's or you may not have one, but the disk does have a protective MBR, it's part of the GUID/GPT spec IIRC. Builtin GUI tools are pretty light on information at times often oversimplified for novice users.

     

    I suspect the Windows changes have already been fixed, especially since you applied your 'fix' that altered the partition tables again in OS X…

    alekseyfromsan francisco wrote:

    To solve the problem, I re-created the partition with DiskUtility in OSX, but choose "OS X Extended (Journaled)" format in step #2. Then after I rebooted in OSX in step #4, it correctly identified the volume as NTFS.

    Editing partition types rewrites the tables.

     

    Testing:

    Disk Utility on a 10.11 install disk (to isolate issues from installed apps on my OS). I am using an admin account inside a 'MSEdge on Win10 VM' https://dev.windows.com/en-us/microsoft-edge/tools/vms/mac/.

     

    Results:

    • OS X converts GPT to a 'hybrid MBR + GPT' partition table when you add an ExFAT volume.
    • Formatting that ExFAT partition to NTFS in Win10 causes the disk to have a damaged GPT table on OS X - only the MBR is left intact, Windows lists it as an MBR not GPT before & after the reformatting.
    • OS X does show an ExFAT & a NTFS volume in addition to the HFS volume - the GPT partition table is in a mess at this point, like you described. gdisk does offer to fix this (sync the MBR to the GPT) but I didn't try that. The NTFS partition appears to be the 200MB EFI volume (yes I did select the ExFAT partition to reformat, but Win10 always changes the EFI partition only).

     

    Notes: I cannot see how to 'delete the partition and re-create it with Windows Disk Manager and formatted with NTFS' as you describe - delete is greyed out. Instead I formatted the filesystem as NTFS in Windows Disk Management.


    Conclusion:

    Ultimately the disks are the same as you described on OS X, two volumes in addition to the HFS+ volume, one ExFAT, one NTFS.

    I suspect Windows wrote an MBR & broke the GUID table. Multiple tests did the same thing, every time, on different disks.

     

    Caveats:

    Maybe I created different results to you by taking the different steps, perhaps deleting is different to formatting, perhaps it is my version of W10 or maybe it is my lack W10 experience, or maybe you never had a hybrid scheme.

     

     

    Now here is where I fall down…

    You say the fix is to 're-create the partition with DiskUtility'. I cannot do that because editing MBR's is not supported on 10.11's Disk Utility.

    I do not know how you did this step, recreating partitions in Disk Utility will normally rewrite the filesystem, so it doesn't make sense to me.

    The option is greyed out in Disk Utility.

     

    If you want to test use another disk or thumb drive, 'gpt' & 'fdisk' will give detail on OS X.

    https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/ man8/gpt.8.html

    https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/ man8/fdisk.8.html

    gdisk is also a good command line third party tool for viewing GUID & MBR partition tables in one place (& seeing if they match).

    http://rodsbooks.com/gdisk/

     

    I have output from fdisk and gpt for each stage if you want to see, it is frankly boring & confusing (I'm not sure about cluttering the thread with it & frankly I have wasted enough time already).

     

    Still think this is an OS X bug? The disk is altered in Windows & the GPT primary partition is deleted from what I can see.

     

     

    P.S. If you really want help with this find Loner T on this site & ask if they will visit this thread & help you. Loner T has excellent GPT/MBR skills & knows more than I do on this topic, I wouldn't backup to a disk setup like this - YMMV.

    Loner T

  • by dialabrain,

    dialabrain dialabrain Feb 14, 2016 7:57 AM in response to Drew Reece
    Level 5 (6,355 points)
    Mac App Store
    Feb 14, 2016 7:57 AM in response to Drew Reece

    Now you see why I said "okay".

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