3 TB GPT partition repair problem

How to use TestDisk to recover lost partition
Forum rules
When asking for technical support:
- Search for posts on the same topic before posting a new question.
- Give clear, specific information in the title of your post.
- Include as many details as you can, MOST POSTS WILL GET ONLY ONE OR TWO ANSWERS.
- Post a follow up with a "Thank you" or "This worked!"
- When you learn something, use that knowledge to HELP ANOTHER USER LATER.
Before posting, please read https://www.cgsecurity.org/testdisk.pdf
Message
Author
Shaping
Posts: 13
Joined: 07 May 2018, 21:28

3 TB GPT partition repair problem

#1 Post by Shaping » 07 May 2018, 21:56

I am trying to repair a damaged partition on a 3 TB RAID 10 drive. The problem seems to have been caused by a power-flicker during boot. I first used Paragon HDM 15 to do an HDD RAW copy from the 3 TB to a new 4 TB drive. When TestDisk analyzed the copy, it found an invalid GPT signature and invalid alt GPT signature. I started the "quick search," but discontinued when I realized it would not be done for days. When TestDisk analyzed the original 3 TB drive, it did in fact find an alt GPT, which I suppose I could use to correct the problem, but i do not want to work on the original drive in case there is a problem, and I must retry. I assumed that the bit copy was not perfect (not likely) or that TestDisk has some target-drive-size logic that prevents it from recognizing the alt GPT in the copy as it did in the original. I'm told that in a cloning no drive ID data is involved.

I then used HDClone 6.0.5 to do the cloning again to the same 4 TB target. I ran TestDisk again and go the same result on the copy.

Is this a TestDisk problem, a target-drive-size issue, or something else?

I'm told that I should create instead an image file for the original drive, repair the GPT partition on the original, and restore the original from the saved image file, if a retry is needed.

Once I get to the actual repairing of the GPT partition, I'm not sure what the best tool is. Can someone suggest one?

Thanks.

Sponsored links

User avatar
cgrenier
Site Admin
Posts: 4286
Joined: 18 Feb 2012, 15:08
Location: Le Perreux Sur Marne, France
Contact:

Re: 3 TB GPT partition repair problem

#2 Post by cgrenier » 09 May 2018, 06:05

The location of the alternative GPT table is linked to the disk capacity.
When you have cloned the disk to a larger one, you have lost this information.
You should use the information from Analyze from the original disk.

If you really want to work on the clone,
- start by using testdisk on the original disk, Analyse, Backup, Quit
- run testdisk on the clone, Analyse, use Load to get the locations recorded by Backup previously, for each partition, set the partition type, on next screen, choose Write, confirm, Quit and restart your computer.

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#3 Post by Shaping » 09 May 2018, 08:58

Thanks for the help. That makes much more sense.

I'm still confused about the following: I did yet another cloning with HDClone, and set the target sector range to match the source range exactly. When the cloning was nearly over, HDClone asked me whether I wanted to make some kind of adjustment on account of the drive-size difference, and I said no, merely confirming what I thought I'd specified earlier with the matching sector ranges. I thought the question was out of place in light of the matching ranges. I must still be missing something.

Going back to the moved alt GPT partition in the original clone on the larger 4 TB, If I had analyzed the original 3 TB drive, and exported/backed-up the parameters, and loaded them into TestDisk on the clone, how can the alt GPT in the clone be moved back to the position found in the original if TestDisk can't locate the alt GPT in the clone? I'm thinking the original parameters don't help TestDisk find the alt GPT in the clone.

Some more background that shouldn't matter, but just in case it does: I was 6% of the way through a DiskCryptor decrypt when the partition was corrupted. I was doing the decrypt after spending many days on the encryption, and discovering at the end that the drive was not accessible in Explorer (yet it was accessible all during the encryption). I assumed that the drive was unhealthy and needed work. The only way to do that was to decrypt; so I began decrypting. I'm assuming that once the partition is corrected (and NTFS is somehow associated with it again), I can resume decryption in DC, so that I can ultimately fix whatever was wrong with drive. DC encryption/decryption is sector-based and orthogonal to partition- and file-system structure. There should not be any problem here. Do you agree?

I did a chkdsk during the encryption and discovered that there were some clusters that needed moving, but there was not enough room on the drive to do that. So the "chkdsk /r" never actually finished the repair. I suspect this is the essence of the health problem.

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#4 Post by Shaping » 13 May 2018, 20:57

After about 5 days, I completed the TestDisk Analysis. I do not see a listed partition. The choices are A: add a partition, L: load backup, Enter: to continue.

Before completion there were several failed attempts to recognize a FAT partition. This is an NTFS partition.
Attachments
TestDisk analyze at 100 percent.png
TestDisk analyze at 100 percent.png (19.01 KiB) Viewed 398 times

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#5 Post by Shaping » 13 May 2018, 21:25

Can someone suggest a next step?

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#6 Post by Shaping » 13 May 2018, 21:33

I hit Enter and see the "No partition found or selected from memory." message and the Deeper Search choice, but I can't select it.

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#7 Post by Shaping » 13 May 2018, 22:31

Below is a screenshot of a second analyze. You can see the basic data partition and how there is no filesystem marker. The partition whose first segment (I think) was corrupted is definitely NTFS. Can I write the marker without deleting the table?
Attachments
Second Analyze.png
Second Analyze.png (35.17 KiB) Viewed 392 times

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#8 Post by Shaping » 13 May 2018, 22:57

I'm currently creating a Backup from the above screen. Is this the correct thing to do now, or should I continue trying to get TestDisk to list a corrupted NTFS partition? This drive is not a boot drive; it's just a data drive.

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#9 Post by Shaping » 14 May 2018, 06:44

The status message below is confusing. I cursored rightward and chose Backup with Enter, but the "Analyze cylinder..." and the check_FAT messages seem to indicate another Analyze is in progress. I do see a backup.log file created at the right time, but it's size is 1 KB, and it hasn't changed for several hours. Is a backup really being created, or is that contingent on finding the right structures on the fly?
Attachments
Backup progress.png
Backup progress.png (22.85 KiB) Viewed 373 times

Shaping
Posts: 13
Joined: 07 May 2018, 21:28

Re: 3 TB GPT partition repair problem

#10 Post by Shaping » 14 May 2018, 22:48

There was a problem with disk space, which is now fixed. I've done another analyze and a backup.log is currently being created. So far this is the contents of the backup.log file:

#1525895149 Disk /dev/sdd - 3000 GB / 2794 GiB - CHS 364794 255 63
1 : start= 34, size= 262144, Id=00, P
2 : start= 264192, size=5860159488, Id=00, P
#1526248285 Disk /dev/sdc - 3000 GB / 2794 GiB - CHS 364794 255 63
1 : start= 34, size= 262144, Id=00, P
2 : start= 264192, size=5860159488, Id=00, P
#1526333682 Disk /dev/sde - 3000 GB / 2794 GiB - CHS 364794 255 63
1 : start= 34, size= 262144, Id=00, P
2 : start= 264192, size=5860159488, Id=00, P

Are we expecting more by the time the backup is complete? Now would be a good time to know. This backup will probably take about 4 days, assuming I've managed to prevent the USB drives from and USB hub from sleeping.

Post Reply

Who is online

Users browsing this forum: No registered users and 0 guests