drive pic

Why would a 4TB drive only be showing up as a 2TB drive?

I have converted the drive to GPT format, but it still only shows as having 1677.90 GB space.


I am using Windows 7 64-bit, so all of this should be possible.

Could one of the platters inside be dead?

Here's a picture of the volume properties:


  • Do you have RAID enabled?
    – Ron Maupin
    Nov 7, 2015 at 2:27
  • If you go to the device properties for Disk 1, what do you see?
    – rakslice
    Nov 7, 2015 at 2:36
  • @RonMaupin - no RAID. This is just a bare drive plugged up to a USB dock.
    – jp2code
    Nov 7, 2015 at 11:52
  • @rakslice: Device properties say "Generic External USB Device" and "This device is working properly." There are other tabs too, but too much info to write it all. What are you looking for? Updated main question with picture from Volumes tab.
    – jp2code
    Nov 7, 2015 at 11:55
  • If nothing else there's a clue in the sizes: 4 trillion bytes, or about 3725 GiB, minus the capacity you see (1677GiB) is 2048 GiB, a conspicuous power of two. So what you're seeing is likely to be the result of a size counter somewhere "rolling over" at 2048GB. This is a 4 platter drive, so the platters are ~ 931 GiB which is hard to get 1677GiB from. =)
    – rakslice
    Nov 7, 2015 at 20:54

1 Answer 1


Your SATA controller that the disk is connected to (for the original asker, a USB SATA dock) currently has a limitation as to how much disk capacity it can address, of 2^{32} 512-byte sectors.

  • Try using the disk with a different SATA controller (for instance an onboard SATA port on your motherboard, or a different USB SATA dock or adapter)
  • Check if the manufacturer of the product the SATA controller is part of provides an updated driver or a firmware update that removes this limitation.


The drive has 7,814,037,168 sectors, but the SATA controller it is plugged into evidently only supports a 32-bit number of sectors for some reason, as the controller's count of the sectors rolls over at 2^{32} (4,294,967,296), and the controller reports to the OS that the drive has 3,519,069,872 sectors. At 512 bytes per sector, this works out to about 1678GB.

  • Thanks! You are absolutely correct. I have 2 different USB docs. One is an older model that would only read 2TB. My newer dock correctly shows the drive as 4TB. Never would have thought of that!
    – jp2code
    Nov 8, 2015 at 0:32
  • Hey, if I create 2 2TB volumes out of this 4TB drive, would the older doc recognize them or would it still have issues?
    – jp2code
    Nov 8, 2015 at 2:32
  • 1
    If the old dock is letting you "see" the first 1677GB of the disk, then if you create a < 1.6GB partition at the beginning using one dock, that partition will work with the other dock and vice versa. But I really wouldn't count on it.
    – rakslice
    Nov 9, 2015 at 22:48
  • My favourite part of the data sheet for this drive is the table in section 2.2, which suggests that the drive provides its 4000 GB formatted capacity with ~ 7 billion 4 kbyte sectors. That's impressive! It's too bad they couldn't cut down on that 567% (22TB) overhead however. =)
    – rakslice
    Dec 8, 2015 at 6:35
  • 1
    I report the same issue with Windows 10: A HDD is detected with lower capacity, 1718168 MB. It happened just after initializing the disk. Before initialization I did, it was detected and partitioned as 4TB. So I suppose if correct initialization is done, issue would be gone. I use USB-SATA adapter. Same issue could happen with 3TB, 5TB, 6TB or any bigger drives. Another USB adapter solved the issue.
    – JRr
    Dec 29, 2020 at 7:02

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