Question PC not seeing 12TB drive properly

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Blitzen

Feb 23, 2025
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Hi all, I hope someone can point me in the right direction about this, as it's doing my head in. I bought a 12TB Seagate IronWolf, slotted it into my external SATA bay, formatted it to 12TB (10.x formatted size), GPT partition, and copied a load of files to it, no problem. However, when I attached it internally to my old 'net PC (i7-4790 / 16GB) Windows would not show the drive contents at all, and drive manager showed a 2tb partition, along with around 9TB unformatted. I assumed it would be the old mobo/chipset/SATA controller at fault, and was going to replace the system soon anyway, so I picked up a cheap i5-8500 PC, bolted it all together, booted up, and it still does the same thing. 😣 Again, it's absolutely fine when in the SATA caddy, but I really need this drive to be online all the time, and not have to fire up the caddy when I want to use it.

Help!

:)
 
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Is the data in the 2TB partition readable when you plug it in internally? How much data were you able to copy to the drive when it was in the enclosure? I assume it's a USB box. Can you actually write more than 2TB to it? It could be the external controller is NOT properly detecting it while the direct SATA port is. (Falsified Seagate drives are big news right now, but it's regarding used drives being sold as new. But maybe there are some being faked as larger than they are.)
 
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evermorex76 said:
Is the data in the 2TB partition readable when you plug it in internally? How much data were you able to copy to the drive when it was in the enclosure? I assume it's a USB box. Can you actually write more than 2TB to it? It could be the external controller is NOT properly detecting it while the direct SATA port is. (Falsified Seagate drives are big news right now, but it's regarding used drives being sold as new. But maybe there are some being faked as larger than they are.)
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Hey, thanks for the reply. Yeah, it's writing (and reading) data no problem when in the external enclosure, in fact I've just written another 3+TB to it tonight. When I plug it into any of the mobo's SATA channels, it doesn't show in Explorer at all, but Diskpart and Drive Manager both agree it's there, but show it as 2TB formatted and 9TB unformatted. There's no chance it's a dodgy drive, I got it and another two identical drives from a customer of ours' data farm (I work for an international ITAD) we get stuff like this all the time.
 
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Blitzen said:
I assumed it would be the old mobo/chipset/SATA controller at fault, and
was going to replace the system soon anyway,
so I picked up a cheap i5-8500 PC, bolted it all together, booted up, and it still does the same thing.
Click to expand...
No. That is fault of your external Sata USB device.
It uses different sector size settings compared to normal settings, when drive is connected internally.

If you change connection type from external SATA USB to internal, you have to repartition and reformat the drive.
 
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SkyNetRising said:
No. That is fault of your external Sata USB device.
It uses different cluster size settings compared to normal settings, when drive is connected internally.

If you change connection type from external SATA USB to internal, you have to repartition and reformat the drive.
Click to expand...
Really? The mobo's SATA controller can't make sense of it because the drive was formatted externally? Wow. Well, if that's all it is, I suppose I'll wait till I've got my new NAS up and running, transfer everything to that, then repartition and reformat it in the PC. Thanks, I'd hoped it wasn't a hardware issue (as such), so this is actually good news, if a bit of a faff.
 
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Blitzen said:
Really? The mobo's SATA controller can't make sense of it because the drive was formatted externally? Wow. Well, if that's all it is, I suppose I'll wait till I've got my new NAS up and running, transfer everything to that, then repartition and reformat it in the PC. Thanks, I'd hoped it wasn't a hardware issue (as such), so this is actually good news, if a bit of a faff.
Click to expand...
Just a case of different cluster sizes.
The external enclosure formatted it one way, internally it wants to be seen as a different way.
Nothing to do with the SATA controller.
 
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I've never had issues with external USB drives being moved to internal. Nothing in that article makes any sense. The explanation of "for compatibility with Windows XP" makes no sense because XP doesn't recognize 4K sectors period,. It will only read 512B native or 512-emulated sectors. There is no way the USB adapter is "changing" the sector size on the fly because the firmware in the drive won't work that way. You have to send SCSI commands to the drive (SATA/NVMe commands) to tell it to switch to presenting 4K blocks which is a semi-permanent change, until you send the command to change back to emulating 512 (which erases your partitioning and data). USB drive controllers don't modify the data going between the OS and the drive, other than the protocol (which may strip data like drive features that aren't supported by USB).
 
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evermorex76 said:
I've never had issues with external USB drives being moved to internal. Nothing in that article makes any sense. The explanation of "for compatibility with Windows XP" makes no sense because XP doesn't recognize 4K sectors period,. It will only read 512B native or 512-emulated sectors. There is no way the USB adapter is "changing" the sector size on the fly because the firmware in the drive won't work that way. You have to send SCSI commands to the drive (SATA/NVMe commands) to tell it to switch to presenting 4K blocks which is a semi-permanent change, until you send the command to change back to emulating 512 (which erases your partitioning and data). USB drive controllers don't modify the data going between the OS and the drive, other than the protocol (which may strip data like drive features that aren't supported by USB).
Click to expand...
Windows XP can see 4K sectors in USB mass storage devices. That's why both Seagate and WD configured their original high capacity external drives with a 4KB sector size. Doing it this way enables Win XP to see 16TiB MBR partitions.

As for changing the sector size on-the-fly, what is really happening is that USB-SATA bridge firmware is communicating with the drive in 512e mode, but is communicating with the USB host in 4Kn mode. It is doing this translation transparently, on-the-fly. When you remove the drive from the enclosure, you expose its native 512e sector size. A SATA host then sees a 4KB file system on a 512e drive. Sector 0 is still in the same place, but every other sector is displaced by a factor of 8.
 
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