Backup Disk Partition Resize = Confusion

Question

Level 1

55 points

Backup Disk Partition Resize = Confusion

I have an external 750 GB FireWire hard disk that I use to back up both my Mac OS X Snow Leopard installation and my Windows 7 installation; it also has a small bootable Leopard partition for troubleshooting. I found myself running out of room for backing up the large iTunes library I have in Windows 7, so I decided to use Mac OS X Disk Utility to shrink the Time Machine partition; then, I used Windows 7 Disk Management to resize the Windows 7 Backup partition. Everything seemed to go fine at first.

Last night I went to back up both systems. The Time Machine backup went fine; however, Windows is showing its backup partition as a RAW partition of its original size, so it won't recognize the existing backup or add to it. When I'm booted in Snow Leopard, the Windows partition appears as NTFS, but there's some confusion: although Get Info shows the partition correctly with its new size, Disk Utility shows the partition with its original size (which is smaller than the size it's claiming is used).

I'm grateful that this isn't messing up my boot drive, but I'd rather not lose the backups that I've already performed (I've done some spring cleaning in my podcast collection, but I'd like to have the ability to go back to the backup if I get too trigger-happy). I don't have room to copy the entire Windows 7 Backup to another disk (it's over 300 GB). Is there any way to correct the GPT / MBR setup to properly recognize the new size of the Windows 7 Backup partition?

Message was edited by: Fahrwahr (apparently Apple Discussions removes the space between paragraph blocks).

MacBook, Windows 7, CD 2.0, 2 GB RAM, 320 GB HD

Posted on May 28, 2013 12:37 PM

Reply

Answer 1

Fahrwahr Author

Level 1

55 points

Jul 19, 2013 3:19 PM in response to Christopher Murphy

I think disk1s2 is the successfully-mounting Time Machine partition. When I open Disk Utility, an unmounted and unnamed disk1s3 shows up as an unmounted partition; Disk Utility lists it as MS-DOS (FAT). The NTFS partition I set up for backing up Windows 7 (which was the original focus of this thread) mounts successfully as well. All three partitions appear when I boot into Windows 7.

Reply

Answer 2

Jul 19, 2013 4:45 PM in response to Fahrwahr

disk1s3 has a GUID partition type set to Microsoft Basic data. So it's for FAT32 or NTFS. What it's actually formatted with, I can't tell you from available information; but often when the type code is wrong, an OS will get confused and not mount the contained file system. It's straightforward to find out what the format really is though:

sudo dd if=/dev/disk1sX count=3 2>/dev/null | hexdump -C

X=the slice/partition number you want to learn about. This command will read the first sector and pipe the data through hexdump so that it's something sorta sensible. If the first line is:

00000000 eb 52 90 4e 54 46 53 20  20 20 20 00 02 08 00 00  |.R.NTFS    .....|

Then it's NTFS.

If the 2nd line is

00000400  48 2b 00 04 80 00 01 00  31 30 2e 30 00 00 00 00  |H+......10.0....|

Then it's HFS+.

The command doesn't change the contents of the disk, it's a read only command. Note that those examples above scroll to the right, what you're looking for is on the far right side. The forum's formatting options are super annoying.

Reply

Answer 3

Jul 19, 2013 4:50 PM in response to Christopher Murphy

Actually if it's JHFS+ your line will be a bit different. I did that in a linux VM, and it creates HFS+ volumes, not JHFS+ volumes. But I think you get the idea. If it turns out that one of those partitions is JHFS+, then the partition type GUID is wrong and needs to be set correctly. Fortunately gdisk can do that.

Reply

Answer 4

Fahrwahr Author

Level 1

55 points

Jul 19, 2013 6:53 PM in response to Christopher Murphy

Here's what I get for the unmounted disk1s3:

00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000400 48 2b 00 04 80 00 21 00 48 46 53 4a 00 00 02 2d |H+....!.HFSJ...-| 00000410 cb 20 d4 4d cd f3 f7 17 00 00 00 00 cb 21 28 ad |. .M.........!(.| 00000420 00 03 06 e0 00 00 b2 c2 00 00 10 00 01 16 66 00 |..............f.| 00000430 00 5f 0e 8a 00 92 8a 73 00 01 00 00 00 01 00 00 |._.....s........| 00000440 00 04 7f 65 00 0c 4d 14 00 00 00 00 02 00 00 0b |...e..M.........| 00000450 00 00 01 00 00 02 c3 2e 00 00 00 00 00 00 00 00 |................| 00000460 00 00 00 00 00 00 01 00 4c 85 47 6e 9b a5 48 9a |........L.Gn..H.| 00000470 00 00 00 00 00 22 d0 00 00 22 d0 00 00 00 02 2d |....."...".....-| 00000480 00 00 80 3e 00 00 02 2d 00 00 00 00 00 00 00 00 |...>...-........| 00000490 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000004c0 00 00 00 00 00 70 00 00 00 70 00 00 00 00 07 00 |.....p...p......| 000004d0 00 00 0a 2e 00 00 07 00 00 00 00 00 00 00 00 00 |................| 000004e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000510 00 00 00 00 09 40 00 00 04 a0 00 00 00 00 94 00 |.....@..........| 00000520 00 04 d6 2e 00 00 94 00 00 00 00 00 00 00 00 00 |................| 00000530 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000560 00 00 00 00 06 f0 00 00 06 f0 00 00 00 00 6f 00 |..............o.| 00000570 00 00 11 2e 00 00 6f 00 00 00 00 00 00 00 00 00 |......o.........| 00000580 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000600

Reply

Answer 5

Jul 19, 2013 7:13 PM in response to Fahrwahr

It's JHFS+. So you need to use gdisk, and change the type code to af00.

sudo gdisk /dev/disk1

t

3

af00

w

y

Reboot.

Reply

Answer 6

Fahrwahr Author

Level 1

55 points

Jul 19, 2013 7:36 PM in response to Christopher Murphy

That brought it back: now I'm back to one NTFS partition and two JHFS+ partitions. Here's hoping that both OSes will be happy with them.

Thanks again for your help!

Reply