I've got a USB hard drive that I've been using with my Mac for backups, formatted as one large HFS+ partition. I added a second NTFS partition for similar use with Windows, as follows:
Resize HFS+ partition using Mac OS X Disk Utility
Reboot into Windows 7 using Bootcamp
Add NTFS volume in the free space using Windows 7 Disk Manager
Now that I've done this, I can see both volumes in Bootcamp Windows, and they seem to be fine.
When I boot into Mac OS X, though, only the NTFS volume appears.
Looking at the disk in Disk Utility, the reason is clear: Mac OS X can't actually see any HFS+ partition there. Its space is shown as "disk4s2", and when I click on it in Disk Utility it's supposedly in "MS-DOS (FAT)" format.
diskutil on the command line has this to say:
~% diskutil list /dev/disk4
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk4
1: EFI 209.7 MB disk4s1
2: Microsoft Basic Data 700.0 GB disk4s2
3: Microsoft Basic Data BACKUPS 300.0 GB disk4s3
Nevertheless, when I reboot into Windows 7, the HFS+ partition pops up again, correct volume label and everything. So clearly the data is still there, and in some kind of usable format.
It's not the end of the world if I have to reformat, but I'd rather keep my full Time Machine history if possible. So is there something I can do to fix this non-destructively, and should I have done something differently when I was adding the second partition?