De-cased 4TB Seagate external drive, partitions not recognized

[lingyi]

It seems Seagate did something to their 4TB Backup Plus STCA4000100 external drives. Withe 2TB & 3TB drives, they could be de-cased and the partitions would be fully recognized when connected directly to the MB or via a SATA to USB dock.

However, a couple of weeks ago removed three of my 4TB drives (purchase late 2013) from their case and when I inserted them into two different SATA to USB docks, the two partitions (2x 2TB) were gone. Drive showed up a single 4TB MBR partition. Put the drive back on the Seagate interface and the partitions are intact!

Anyone else experience this? I've de-cased multiple 1, 2 and 3TB externals in the past and this is the first time I've seen this happen.

I changed the drives to GPT, set to two 2TB partitions and recopied everything since I was planning to reorganize my movies anyway.

FYI, I prefer two, 2TB partitions because it makes it easier to manage and backup my mix of 4, 6 and 8TB drives.

Edit: I didn't try connecting the drives directly to the MB since I was planning to use them in a different external case anyway.

[Robbo74]

Having the same issue with the same 4TB drive, and like your situation any drive smaller in capacity swaps out just fine. Although in my situation I may have to buy another Seagate enclosure because the USB3 riser off the board has long been separated from its home and MIA so I cant even attempt to solder the POS back on. There must be some sort of proprietary business on the board itself for the drive to be recognized without any sort of setting change in my bios or any additional patch etc...The only thing Im wondering about is if I can just buy another Seagate case and plop my drive into it and expect to see all my beautiful beautiful mubies n data n patches n the such in its entirety? Or is there some way to view my data without buying a whole new case , as in simply plugging my drive into SATA to USB adapter and change a setting or two in MMC?

[Bjs]

Used to break the drives down into partitions to overcome specific issues / system limits ... even manufacturers drive setup software would do the same thing if specific limits of the system were detected.

Only GPT would be recognised directly connected to the system ... reporting a single MBR partition would have been a bug from a system limit, nothing more

Ms article 2581408

[lingyi]

Having the same issue with the same 4TB drive, and like your situation any drive smaller in capacity swaps out just fine. Although in my situation I may have to buy another Seagate enclosure because the USB3 riser off the board has long been separated from its home and MIA so I cant even attempt to solder the POS back on. There must be some sort of proprietary business on the board itself for the drive to be recognized without any sort of setting change in my bios or any additional patch etc...The only thing Im wondering about is if I can just buy another Seagate case and plop my drive into it and expect to see all my beautiful beautiful mubies n data n patches n the such in its entirety? Or is there some way to view my data without buying a whole new case , as in simply plugging my drive into SATA to USB adapter and change a setting or two in MMC?

I've swapped out and used the dock with other drives (including non-Seagates and I'm currently running a 2TB WD in a Seagate case) so you should be fine getting another Seagate external and using the dock.

Can't try it myself since I've already re-partitioned my drives, but try mounting the drive in Linux (you can use boot a live distro for a quick test). If Linux can't recognize the drive, it's unlikely Windows will. Good luck!

[hello_hello]

Could I ask the obvious, or maybe the not so obvious..... are you sure the USB docks support drives larger than 2TB? That's a fairly recent thing, despite the availability of larger than 2TB drives for a fair while. Some USB docks sold today still have a 2TB limit.

You might have a USB enclosure doing 4K sector emulation, which I don't quite understand, but it possibly explains why you see a 4TB MBR. Halfway down this page the person testing USB bridges speculates:
But the reasons are straightforward – there may be a limitation to the number of blocks a USB Mass Storage device can report, and older machines running Windows XP can now use these larger drives with MBR partitioning because the number of blocks (where each block is 4kB rather than 512 bytes) is now less than the 32-bit limit.

And even docks supporting drives larger than 2TB can apparently get in on the act, so that's something to watch out for.
http://plugable.com/2013/03/21/understanding-large-sata-drive-compatibility
Some docks have a non-standard sector emulation feature that enables using capacities above 2TB on Windows XP 32 bit. But this requires that drives initialized and formatted in a special way, and NOT be used with other SATA controllers in desktop PC’s or other drive docking stations, unless those units also have a matching firmware version and support for this feature.

I'm not sure if it's as simple as creating 2TB partitions for older OSs. XP has a 2TB limit no matter how large the drive is so any capacity over 2TB would at best be wasted, however I've had no issues accessing the full capacity of 3TB and 4TB USB drives with XP. There's obviously still some sort of translation going on when USB enclosures use drives with 2TB partitions as the computer only sees a single large partition, but I can't remember if that works the same way. If I ever really knew.....

[lingyi]

Could I ask the obvious, or maybe the not so obvious..... are you sure the USB docks support drives larger than 2TB? That's a fairly recent thing, despite the availability of larger than 2TB drives for a fair while. Some USB docks sold today still have a 2TB limit.

You might have a USB enclosure doing 4K sector emulation, which I don't quite understand, but it possibly explains why you see a 4TB MBR. Halfway down this page the person testing USB bridges speculates:
But the reasons are straightforward – there may be a limitation to the number of blocks a USB Mass Storage device can report, and older machines running Windows XP can now use these larger drives with MBR partitioning because the number of blocks (where each block is 4kB rather than 512 bytes) is now less than the 32-bit limit.

And even docks supporting drives larger than 2TB can apparently get in on the act, so that's something to watch out for.
http://plugable.com/2013/03/21/understanding-large-sata-drive-compatibility
Some docks have a non-standard sector emulation feature that enables using capacities above 2TB on Windows XP 32 bit. But this requires that drives initialized and formatted in a special way, and NOT be used with other SATA controllers in desktop PC’s or other drive docking stations, unless those units also have a matching firmware version and support for this feature.

I'm not sure if it's as simple as creating 2TB partitions for older OSs. XP has a 2TB limit no matter how large the drive is so any capacity over 2TB would at best be wasted, however I've had no issues accessing the full capacity of 3TB and 4TB USB drives with XP. There's obviously still some sort of translation going on when USB enclosures use drives with 2TB partitions as the computer only sees a single large partition, but I can't remember if that works the same way. If I ever really knew.....

Interesting points.

Neither of the extenal devices I tried (MediaSonic Probox HF2-SU3S2, Sabrent SATA to USB dock) have any problem with any other SATA drive up to 8TB so I forgot about the possibility of the 2TB limit. I do have a genera SATA / IDE to USB adapter that won't work with >2TB drives so I haven't used it in years.

IIRC, out of the box, the drives were pre-formatted as one large 4TB MBR partition and the included dock was required for it to be recognized. I think the 3TB WD externals had the same issue (don't really remember, it's been years since I've had one). Oddly, 2TB & 3TB Seagates were fine. I have an 5TB Seagate Expansion drive, but I won't be opening that one up until 2017 when the warranty expires.