macos - NTFS partition created in OSX won't show up in Windows

I have a 3TB external drive that I recently partitioned and formatted to use to backup all my various computers -- two partitions, one NTFS and one HFS+. I did the initial setup using Disk Utility on an iMac, backed that up, then proceeded to back up 2 other Macs in the house.

Now, I'm trying to backup my Windows laptop, but the NTFS partition is not showing up. In my Disk Management console, it shows the disk with 4 partitions:

• 200MB "GPT Protective Partition"


• ~2TB "RAW" (this should be NTFS)


• ~1TB "RAW" (This is actually HFS+)


• 127MB Unallocated (Disk Utility didn't mention this...)

Of course, the NTFS partition shows up fine on all the Macs, provided they have NTFS-3G installed.

Here's the thing that might be throwing Windows off:

DISKPART> detail partition
Partition 2
Type  : 0B
Hidden: No
Active: Yes
Offset in Bytes: 210763776

Note the Type: 0B -- that's FAT32, though Disk Utility clearly lists it as NTFS.

Did NTFS-3G create the partition wrong? Is there a way to fix this without losing the data on the partition? I'd really like to make a backup of this Windows laptop pretty soon...

Answer

The problem is the default partition scheme used by the Mac when you created the partitions. Mac OS X uses map scheme GPT (GUID Partition Table, EFI compatible), that's why there's a GPT partition .

Windows likes MBR (Master Boot Records) a lot - and Mac OS X can handle them as well. So you have to re-partition you external harddrive (you loose all the data, or buy iPartition - it can change partition schemes without loosing the data).

If you partition this drive in Mac OS X with Disk Utility be sure to click 'Options' in the 'Partition' window. There you can choose from 'GUID Partition Table', 'Apple Partition Map' and 'Master Boot Record'. And the last one is what you want.

Afterwards Windows (and Mac OS X too) will see the NTFS partition.