Diskpart seems confused as to disk size - but only sometimes

Hello everyone,

I've come across a weird problem that I'd like to share with you: under certain circumstances, Diskpart and some other programs don't report the correct capacity of a hard disk.

The disk in question is a new 4 TB, or 3.64 TiB (3762 GiB), Seagate BarraCuda, initalized as a GPT disk with one partition, covering the whole of the disk. I'm using it as a data disk, D:, in an Optiplex 330 PC, running 32-bits Windows 10-1830.

What happens when I boot the PC normally, is that Diskpart reports a disk size of 1678 GiB, containing one partition of 3762 GiB. Come again? Yes, that's right: the partition is more than twice the size of the disk it's on. Two partition manipulating programs, Minitool Partition Wizard and AOMei Partition Assistant, both see the disk as having a size of 1678 GiB, and one partition of the same size. So they partly agree with Diskpart. Minitool as well as AOMei report way too few cylinders and physical sectors, which might explain where they get their sizes from - or the other way around. The number of cylinders reported is 219051, whereas it shoud be 486401; the mumber of physical sectors reported is 3519069872, which should be 7814037168.
However, Disk Management, Chkdsk and Explorer all agree that the disk and its partition are 3762 GiB.

It gets stranger. If I boot the Optiplex with a Win 10-1709 recovery USB, made on the Optiplex some time ago, all programs agree that the disk and its partition have a size of 3762 GiB, with the correct number of cylinders and physical sectors. If I connect the disk to a USB port of the Optiplex or another PC via a docking station, I get the same results. If I put the disk in another PC as drive D: , all programs agree as well: 3762 GiB, nothing wrong.

So what is going on here? Nothing seems wrong with the disk or with the Optiplex's SATA controller, as the disk is read correctly when booting with a recovery USB. It's as if there is some wrong information floating around in a hidden corner of Windows, which rears its ugly head whenever the disk in question is hooked up.

Maybe it's nothing, but I don't like discrepancies like these - they make me distrust my hardware. It's like there's a ticking time bomb that can go off any minute, making the disk unreadable. So I'd like to correct it! What I've already tried, is:
- wiping the disk clean with Diskpart and re-partitioning it;
- cloning the disk (sector-by-sector copy) from a known good identical twin in a docking station.
Neither attempt had any effect, which strengthens my idea that it's not the disk that's at fault here. But then, what is? And how do I put things right?

Any ideas on how to go about this will be greatly appreciated.

Regards, Jaap.

Jaap Verhage said:

Hello everyone,
[Snip]
What I've already tried, is:
- wiping the disk clean with Diskpart and re-partitioning it;
- cloning the disk (sector-by-sector copy) from a known good identical twin in a docking station.
Neither attempt had any effect, which strengthens my idea that it's not the disk that's at fault here. But then, what is?

Regards, Jaap.

You did clone from a disk and partition of identical size, right?

titetanium said:

You did clone from a disk and partition of identical size, right?

I did. The two disks and partitions are identical.

I don't know what to tell you. This type of thing usually is the result of trying to clone mismatched disks and partitions. The only other thing I can think of is instead of cloning, you could try a clean install and copy everything over from the original working disk and partition. Or used macrium reflect to backup the original partitions and then restore them to the new disks via usb flash drive.