Why does my 3TB external drive show as "unallocated" when installed internally? [duplicate]

Question

I have a Seagate 3TB drive with a USB 2.0 interface on it. I took it out of the case and installed into my PC (SATA). Physically, it’s like any other hard disk drive.

But all that Windows wants to do is format it. Even the Seagate utility “DiscWizard/Extended Capacity Manager” shows a small .34TB partition in the front (none of these are usable in Windows), then 1.66TB unallocated, then .73TB unallocated.

Looks like it’s offering the first 2TB as one unit, and the rest as another. I get that, but why is it unallocated? There’s definitely usable data on there, which I just saw when it was in the enclosure.

I’m on an ASUS F2A85-V PRO FM2 "AMD A85X (Hudson D4) 7 x SATA 6Gb/s USB 3.0 HDMI ATX" motherboard, and my older drive with Windows 7 is legacy, not UEFI.

Windows 7 shows the BIOS mode as “Legacy.” But I thought it wasn’t a requirement to boot via UEFI to use a data drive (non-boot) over 2TB.

I also have a 4TB that I’d love to put in my new big case, but while I’ll risk wiping the 3TB, I won’t play around with the 4TB until I figure this out.

Answer 1

Most of the massive external hard drives are configured with 4KB LBAs (Logical Block Addresses), which would cause an issue like yours when plugged internally via SATA. Removing the enclosure exposes the HDD to its native 512e LBAs (which are typical for internal SATA drives). This is due to the fact that SATA ports on the motherboard use such native 512-byte LBAs. I’m afraid that you’d be able to access your data only if you have the drive in an external enclosure.