Recover a GPT Partition that became RAW in 3T Internal HDD

OK, that means PW sees only 746GB. And that is not even your full first data partition which is 1TB ( approx 1565565871 sectors.)

Now this 746GB seems to be a magic number . If you google 3TB GPT HDD only shows 746GB Raw, you get hundreds of user queries. But they all mean it shows only 746GB in Windows Disk Management. Here it is the reverse. Windows Disk Management shows full 3TB but everything else shows 746 GB. Baffling.

I am now thinking of the following course of action/s.

1. All this started after you reinstalled Windows 7 on a new SSD. The original System HDD is now a secondary drive. Can you go back to the original system? That is take out the SSD, and boot from the HDD as before. See whether all the data partitions on your 3TB disk come alive as before.

2. Use TestDisk for DOS. Make a dos bootable pendrive, boot from it. ( That way Windows does not come into play) If TestDisk sees your full 3TB drive with all 3 data partitions visible, we can possibly recover all data from the first data partition.

Before executing any of this plan, you have to copy all data from the now visible data partitions to another disk. Once we recover the data from the first data partition, you can put the SSD back, wipe the 3TB HDD clean, format it and see whether the full disk is visible without any problems.

Give these propositions a thought and let me know.

I would also elicit dsperber's thoughts on this or any other plan of action since he has been evincing a keen interest on this thread. In yesteryears I had many experts like Slartybart, Anshad Edavana and Kaktussoft chipping in giving valuable support and ideas and many times they made up for my deficiencies but now I am trudging alone.

I am retiring soon today and I shall see you here tom.

The devil returns.

"What do you think of using bootrec /fixboot from win recovery dvd."

That is only for fixing the System disk. You can't apply it for non-system disks.

"i was thinking that once i dont have any backup of the MBR/Boot Sectors i can't try to restore it from there but what if we could locate the duplicate of Partition Boot Sector and get information from there."


Your 3TB GPT drive has its protective MBR at sector 0. And this protective MBR will be the same for all GPT drives

Below is a screenshot of the protective MBR.( This drive was initialised as a GPT drive using Windows Disk Management)



The 16byte green highlighted string is the partition table for a 2TB partition. GPT-unaware programs will read the disk as a 2TB MBR drive so that you know " OMG! this program does not recognise my GPT disk and desist doing any disk operations with it that may muckup and corrupt the GPT partition data.

The four bytes orange highlighted string is the unique ID ( disk signature). It can be any four byte hexadecimal like 0A AA FE 09. No need to bother about this unless the system reports a "signature collision"

Check sector 0 of your 3TB drive with bootice. If it is not the same edit the fields as in the above screenshot and save it to disk. Save the sector before editing so that you can restore it if need be.

Using bootice: My post #7 here: Lost partitions!

( I would think that your disk's protective MBR is not corrupted. To my knowledge if the protective MBR is corrupted the whole disk will become RAW.)

Exercise caution to perform this on the correct disk.

To be continued after a break.

Continuing.......

This morning I was able to fishout a brand new Seagate 3TB Expansion Desktop drive - factory formatted - from my daughter's cupboard and made three 1TB partitions in it.



If one is going to use a disk only as a data disk, what all is needed in the protective MBR at sector 0 is the 16byte 2TB partition table and the Boot Record Signature 55 AA at the end. ( The 4byte Unique ID also known as Windows Disk signature can be any hexadecimal number including 00 00 00 00)

But if one is likely to use it as a bootdisk anytime, he will be better off wiping sector 0 and initialising it as a GPT with Windows Disk Management with the resulting Sector 0 as in the screenshot in the previous post.

Now coming to the partition structure and its backup:

Sector 1 - The GPT header. Its backup is at the last sector n-1. The backup however is not an exact replica of Sector 1 It is recoded to make the system believe it is coming from Sector 1

If I denote the total sectors shown in bootice as n then the backup is at sector n-1. Here n=5860533167 ( If you start counting from 1, the last sector is actually n-1 and accordingly the last sector will be shown as 5860533166 in the bootice sector field on top )





Sector 2 - Partition Tables ( each sector can accomodate 4 partition tables.) Here tables for the 128 MB MSR partition and the three data partitions. Its backup will be at sector n-33 =58605333134. The backup is an exact replica of Sector 2





Sector 264192, Sector 1953685504, Sector 3907184640 Volume Boot Records for the three data partitions at its start sector. (MSR is not user accessible and used by the OS to store data when needed. No VBR)

One Data partition VBR sample:




If the GPT Header and the partition tables get corrupted, the system will automatically read from the backup and the disk will continue to perform normally. The user wouldn't even know that some corruption had taken place and the partition data is being read from its backups.

( The corrupted header/Partition Tables will continue to remain as such in their seats. They are not restored with the backups)

Will be continued after a short break