How to rebuild Mac partition showing unexpected GPT table size

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I'm attempting to rebuild a Mac partition for an external 3TB Hitachi hdd that recently failed to mount. Apart from an unexpected GPT table size which I'll show later, this drive issue seems similar to How to fix Mac hard drive partition showing as Fdisk_partition_scheme.

Here is some background and info. on the drive I've gathered:

Since the drive's enclosure appeared to have a loose connection, it was given a new enclosure. As a precaution and to have a working copy, dd was used to create an image of the entire 3TB drive. For any steps that require a device as input, I attach the image using hdiutil attach -nomount path/to/file.dmg.

The drive was originally formatted with a single partition using Mac OS X Snow Leopard. I found the HFS+ partition type GUID while scanning through the data in the hex editor, Hex Fiend:
53746F72-6167-11AA-AA11-00306543ECAC (Apple Core Storage Container HFS+ FileVault volume container). This was followed by the 1st EFI part entry is at offset 4096:

The 1st EFI system partition is at offset 8192:

I attempted to extract the GPT/EFI and HFS partition information from the above image:

06 00 00 00 00 00 00 00 = 6 (start of EFI).

05 C8 00 00 00 00 00 00 = 51205 (end of EFI).

06 C8 00 00 00 00 00 00 = 51206 (start of HFS).

6F 94 A9 2B 00 00 00 00 = 732533871 (end of HFS).

The secondary EFI system partition at offset 3000592957440 appeared to contain the same start and end values, and the secondary EFI part entry was at offset 3000592973824.

The 1st HFSJ entry was found at offset 209740800:

The total # bytes given by diskutil info is 3000592982016:

If the HFS main volume size is 732533871 – 51205 = 732482666 blocks, then the logical block size should be 4096 (which gives total # blocks on disk = 732566646). Although a 512 byte block size was given by diskutil info (above image).

Unfortunately gdisk couldn't read the GPT data:

GPT fdisk (gdisk) version 1.0.4 
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: not present

This is what I used as an attempt to start to rebuild the GPT partition table (following How to fix Mac hard drive partition showing as Fdisk_partition_scheme):

sudo dd if=/dev/zero of=/dev/disk2 bs=512 count=40
sudo gpt create /dev/disk2

Then I ran sudo gpt -r show /dev/disk2, which gave an unexpected GPT table size:

  start   size  index  contents
  0      1         PMBR
  1      1         Pri GPT header
  2     18         Pri GPT table
 20      1
 21     18         Sec GPT table
 39      1         Sec GPT header

After the above GPT utility results, I wasn't sure which logical block size to use to rebuild the EFI and HFS partition tables.

Thanks for any help!

1/31/2020 Update

I finished using rsync to make another 3TB disk image copy (I've been keeping the original disk image that was created via dd as a backup).

I think I located the 3rd partition at offset 3000458738688 bytes (it was the 1st data string following the end of the HFS main volume). It appears to end either at offset 3000582143352 or 3000582143360 (any input on this is appreciated):

Unlike EFI/GPT and HFS, there didn't appear to be start or end addresses in any headers that I could extract for this 3rd boot partition. Note that I added larger partition images to show this. So I'll try using the above estimated byte offsets (converting to sectors/blocks) as input for the 3rd gpt add step.

Thanks again for any feedback!

Best Answer

Based on the latest information posted in the question, here is what to enter. The assumption is the values posted are correct. The drive used a 4096 sector size. Since image files are fixed at a 512 byte sector size, all the values need to be multiplied by 8.

Note: You may get an error message when entering the command to destroy the GPT. You should ignore this message.

sudo chown $USER:staff path/to/file.dmg
hdiutil attach -nomount path/to/file.dmg
gpt destroy disk2
gpt create disk2
gpt add -i 1 -b $((6*8)) -s $(((51205-6+1)*8)) -t efi disk2
gpt add -i 2 -b $((51206*8)) -s $(((732533871-51206+1)*8)) -t hfs disk2
diskutil mount disk3

The GPT you posed has a partition type GUID for Core Storage, but the header you posted for this partition indicates the partition type GUID should be for a Hierarchical File System Plus (HFS+) partition. My answer assumed the header is correct.

References

The 16,384 byte size requirement for the GPT Partition Entry Array is defined in section 5.3.1 "GPT overview" on page 117 of the Unified Extensible Firmware Interface (UEFI) Specification version 2.8, March 2019.

Technical Note TN1150: HFS Plus Volume Format

GUID Partition Table

Related Solutions

MacOS – How to i recreate the Partition Table

Ok i managed to boot my osx partition again.

To find the hidden partition i created a bootable OSX Mavericks installation on an external harddrive on which i installed TestDisk.

TestDisk scanned my builtin HDD for partitions and created the output seen in the question.

To restore the table gdisk with the given sectors gdisk was used.

I think I messed up the Fusion Drive on the 1TB iMac (with BootCamp)

Theoretically everything is fine with your Fusion Drive. Fusion Drives look like this. Disk0 is your SSD with 121 GB and disk1 is your HDD with ~1 TB (~1.121 TB summed up).

The larger parts of your SSD (disk0s2) and your HDD (disk1s2) are pooled to a CoreStorage LVG (Fusion Drive: disk3) with a size of 967.8 GB. The rest is reserved for EFIs, a Recovery HD (alltogether ~1.3 GB) and your old Windows partition - now probably free space (~152 GB).

The logical volume 'Macintosh HD' (967.8 GB) spans disk0s2 and disk1s2. This is the first 'Macintosh HD' in picture 1. The volume 'Macintosh HD' - it's the one visible on the desktop - should ideally also have about 967.8 GB. This is the second 'Macintosh HD' in picture 1.
In fact it has only 852.67 GB (see picture 3).

In the second picture the logical volume 'Macintosh HD' is the first listed in black, the volume 'Macintosh HD' is the second listed in black, the other two 'Macintosh HD's listed in grey are the parts of your SSD and HDD dedicated to the logical volume 'Macintosh HD'.

In my opinion something went wrong after deleting various partitions with the Bootcamp Assistant/Disk Utility or in Windows.

Preparation:

Detach any external drive (especially your external Time Machine backup drive)
Restart to Internet Recovery Mode by pressing alt cmd R at startup.
The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated.
On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot into a recovery netboot image which usually is loaded from an apple/akamai server.

I recommend ethernet because it's more reliable. If you are restricted to WIFI and the boot process fails, just restart your Mac until you succeed booting.

Alternatively you may start from a bootable installer thumb drive (preferably Mavericks or Yosemite) or a thumb drive containing a full system (preferably Mavericks or Yosemite).

Now you may either repair CoreStorage or rebuild your Fusion Drive:

'Repair CoreStorage' (not recommended):

First i would try to check the volume 'Macintosh HD' with Disk Utility. If the volume is corrupted consider a reinstall of Mac OS X.
If the volume is ok quit Disk Utility
Open Terminal and enter diskutil unmountDisk /dev/LVIdentifier and both diskutil unmountDisk /dev/DiskContainingApple_CoreStorageIdentifier
In your case: first diskutil unmountDisk /dev/disk3 then diskutil unmountDisk /dev/disk0 and diskutil unmountDisk /dev/disk1
remove the EFI NO NAME partition with gpt remove -i IndexNumberOfEFINoName DiskIdentifier:
gpt remove -i 4 disk1
Remount the CoreStorage disks and then the Logical Volume:
In your case: first diskutil mountDisk /dev/disk0 and diskutil mountDisk /dev/disk1 and then diskutil mount /dev/disk3.

enter gpt -r -vvv show /dev/diskIdentfierOfApple_CoreStorage to get infos of your HDD CoreStorage disk.
In your case: gpt -r -vvv show /dev/disk1
It should look like this:

-bash-3.2# gpt -r -vvv show /dev/disk1
gpt show: /dev/disk1: mediasize=1000204886016; sectorsize=512;         blocks=1953525168
gpt show: /dev/disk1: PMBR at sector 0
gpt show: /dev/disk1: Pri GPT at sector 1
gpt show: /dev/disk1: GPT partition: type=C12A7328-F81F-11D2-BA4B-00A0C93EC93B, start=40, size=409600
gpt show: /dev/disk1: GPT partition: type=53746F72-6167-11AA-AA11-00306543ECAC, start=409640, size=1671210848
gpt show: /dev/disk1: GPT partition: type=426F6F74-0000-11AA-AA11-00306543ECAC, start=1671620488, size=1269760
gpt show: /dev/disk1: Sec GPT at sector 1953525167                               
     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    1671210848      2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
1671620488       1269760      3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
1672890248     280634887
1953525135            32        Sec GPT table
1953525167             1        Sec GPT header

The free space on your HDD has 280634887 blocks. Please calculate the biggest block number dividable through 8. That's 280634880 blocks (á 512 bytes) which equals 143685058560 B or ~143.7 GB. Add the size of your HDD CoreStorage Physical Volume (852666400768 B) The result is 143685058560 B + 852666400768 B = 996351459328 B
Resize your HDD CoreStorage physical volume with diskutil cs resizeDisk HDDPVUUID newsize
In your case: diskutil cs resizeDisk 93892BE8-2B7F-4ABD-A4C3-984495DCD98D 996351459328b
Calculate the maximal size of your CoreStorage Logical Volume in diskutil cs list: (size disk0s2) + (size disk1s2) In your case that's 120988852224 B + 996351459328 B = 1117340311552 B. That should be the size of your refreshed Logical Volume Group.
Resize your Logical Volume with diskutil cs resizeVolume LVUUID LVGSize-128 MB In your case that's diskutil cs resizeVolume D237FFDC-7DA4-41D7-AC13-4CC7E5E8C0A0 1117212311552b. If you get an error (There is not enough free space...) choose a smaller size like 1117148311552b.
Quit Terminal and open Disk Utility.
Check your expanded CoreStorage Volume for errors.
Quit Disk Utility, choose your CS volume as startup disk and restart your Mac

'Rebuild Fusion Drive' (recommended if you have a Time Machine backup)

Booted to Internet Recovery Mode open Utilities → Terminal in the menubar and enter:
diskutil cs list to get the CoreStorage listing.
Copy the Logical Volume UUID, it's the fifth listed.
Now delete the Logical Volume with diskutil cs deleteVolume LVUUID.
In your case: diskutil cs deleteVolume D237FFDC-7DA4-41D7-AC13-4CC7E5E8C0A0.
Copy the Logical Volume Group UUID, it's the first listed in the listing of diskutil cs list.
Then delete the Logical Volume Group with diskutil cs delete LVGUUID.
In your case: diskutil cs delete 1EFE58BC-3613-44C4-86EE-D816F3B66E3E
Enter exit and quit 'Terminal'
Open 'Disk Utility'. Enter 'Ignore' if you are asked to fix the drives.
Choose your SSD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
Please check that the size is ~121 GB

Example:
Choose your HDD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
Please check that the size is ~1 TB

Example:
Quit Disk Utility and open Terminal
Enter diskutil list

Example (your disk identifiers and sizes are different of course: Your volume SSD probably has the Identifier disk0s2 and the size 121 GB and your volume HDD probably has the Identifier disk1s2 and the size 1.0 TB):
Enter diskutil cs create "Name" IdentifierSSD IdentifierHDD
In your case probably diskutil cs create "Macintosh HD" disk0s2 disk1s2.

Copy the resulting LVGUUID

Example:
Enter diskutil cs CreateVolume LVGUUID jhfs+ "Macintosh HD" 100%.

Example:
Enter diskutil cs list
Check the size of your Logical Volume. It should have the size ~1.121 TB

Example:
Quit Terminal
Open 'Disk Utility' and check your newly created volume for errors
Quit 'Disk Utility'
Attach your external Time Machine backup drive or check this answer if you use NAS or another network share.
Open 'Restore from Time Machine Backup'
Choose the appropriate Time Machine backup and restore your system
Reboot to your restored system.
Unmount and detach your Time Machine backup drive
Open 'Terminal' and enter 'diskutil list'
Check if your 'Recovery HD' is listed.
If your 'Recovery HD' is missing, usually reinstalling your current system with the latest available system installer (e.g. 'Install OS X Mavericks (10.9.5)' if Mavericks is currently installed) will recreate it without loosing any data. AFAIK Recovery Partition Creator 3.8 will NOT create a Recovery HD on CoreStorage volumes.
After reinstalling the system with the latest available system installer open App Store and install the latest security fixes.