I have a 4TB Seagate drive, model ST4000DX002, that is showing up as a 1.8TB drive when I plug it into either a Windows, Mac, or Linux system.

Using TestDisk in Linux, I was able to locate the partition and create a raw image from it, but the image size is 1.8TB in size.

Any advice is appreciated.

Do you use older USB adaptor ? Which doesnt support 4k sector size?

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Angel Data Recovery

That is possible. I didn't think of it. I will hook it directly into the system (live booting into Linux) and will post an update.

The problem appears to be a 32-bit LBA limitation. A capacity of 4TB requires 33 bits to report the total number of LBAs (512e mode). An adapter, or BIOS, or SATA driver that has a 32-bit limit will discard the uppermost bit.

4TB - 2TiB = 1.8TB

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A backup a day keeps DR away.

@DR-Kiev and @fzabkar, that was definitely the problem - the USB to SATA adapter had a 32 bit limit. I have a 3.7 image file to work with now. Thank you for the advice, it's much appreciated.