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Hi folks,

I tried to use a 3Tb drive in a USB3.0 external case from Windows 10 yesterday, and it was not mounted. Per the Disk Management tool, the partition table had been changed - instead of the full drive, I had a
2048 Gb partition and some unused space. I don't recall whether I had used MBR or GPT partitioning on this drive.

I tried a worthless commercial solution with no happiness, then I found testdisk. testdisk permitted me to see the FLAC music files and copy them off, though I had 299 errors after the copy was finished and
don't see the filenames that failed in the log. But I got the vast majority of my data copied, which is a lifesaver - thanks for this tool! I do wish I knew what files were a problem.

When I try to fix the partition table, it's close but not quite right. testdisk clearly knew the right NTFS size and contents, but when I write the partition table (I think I tried to write a primary partition) and
rebooted, Windows 10 File Explorer shows my "H:" partition, but says I must format it before I can use it. The Disk Management tool shows a 129 Mb unallocated slice and a 2794.39 Gb Healthy Basic Data Partition,
and seems to be using GPT. It is unclear to me why Win10 is unhappy with this newly-written partition information.

Does anyone have ideas? Could this be MBR vs. GPT confusion? Do I have to let Windows go ahead and format it?

Thanks,
Rob T

rthurlow wrote: 31 Aug 2021, 18:44 Hi folks,

I tried to use a 3Tb drive

HDD? SSD? Product name? Purchased naked without any housing? Extracted from an external housing?

in a USB3.0 external case

Was that a case that was empty and supposed to be filled with a drive?

from Windows 10

"from windows"???

yesterday, and it was not mounted.

Which operating system did you use?

Per the Disk Management tool, the partition table had been changed - instead of the full drive, I had a 2048 Gb partition and some unused space.

This could have happened because you removed that drive from a location with some interface electronics.

I don't recall whether I had used MBR or GPT partitioning on this drive.

I tried a worthless commercial solution

Which one?

with no happiness, then I found testdisk. testdisk permitted me to see the FLAC music files and copy them off, though I had 299 errors

A single number of errors would have been already reason enough to duplicate the drive as described in the manual, maybe preceded by checking SMART parameters.

after the copy was finished and
don't see the filenames that failed in the log. But I got the vast majority of my data copied, which is a lifesaver - thanks for this tool! I do wish I knew what files were a problem.

When I try to fix the partition table, it's close but not quite right. testdisk clearly knew the right NTFS size and contents, but when I write the partition table (I think I tried to write a primary partition) and
rebooted, Windows 10 File Explorer shows my "H:" partition, but says I must format it before I can use it. The Disk Management tool shows a 129 Mb unallocated slice and a 2794.39 Gb Healthy Basic Data Partition,
and seems to be using GPT. It is unclear to me why Win10 is unhappy with this newly-written partition information.

It is unclear to me why you would want to continue using a drive with 299 read errors.

Does anyone have ideas? Could this be MBR vs. GPT confusion? Do I have to let Windows go ahead and format it?

Formating does not recover anything but is deleting stuff.

The 3TB drive is an HDD, a Western Digital WD30EURX. It was purchased as a bare drive, and was in an external USB 3.0 case when I noticed the problem, and I moved it inside my Dell to troubleshoot it and have been working on it in there. The external case is a Seagate Desktop Expansion Drive whose original drive died a couple of years ago. All of my tinkering on this front has been on my Dell 8930 running Windows 10.

I don't know the nature of the errors during testdisk's file copy, so I am not going to assume the drive is toast without some more data. If I can restore the partition correctly, I should be able to check the data more carefully and find out what failed, and also do a surface test with Spinrite. It sounds like you suspect I might have more success putting it back in the Seagate case, which is a good suggestion which I will try - thanks!

Rob T

Your external drive might contain some electronic interface that translates a sector size of 512e into 4096 to break the 2TB barrier. When moving that into your Dell machine there is no conversion anymore and the sector size drops back to 512e.
That might be an issue.

@recuperation, you're exactly right. I put the drive back in the Expansion Desk case and re-ran testdisk, and after rewriting the partition table and rebooting, Windows 10 shows all of my files. I will do more tests on the integrity of the drive, but I'm very happy to see my files back. Thank you for the clarifying questions and the suggestion!