Why is my USB drive showing corrupted data when plugged as an internal SATA drive?

I have a 3TB Seagate Backup Plus Desktop USB 3.0 drive, which works fine when in its enclosure, but when I get it off its enclosure and directly plug it as an internal SATA drive, it's just not properly recognized (it works again when used in the enclosure).
My systems’s motherboard is an ASUS P8P67 LE, which has two SATA 6.0 Gb/s and four SATA 3.0 Gb/s ports.

When used as an internal SATA drive Windows 7 asks if I want to format the drive, as if it didn’t have a proper filesystem, and if I use the DISKMGMT.MSC tool (typing that in the start menu) I get completely wrong information about the drive.

It says the drive has 3 partitions (349,31GB of RAW data and two unassigned partitions of 1698,68GB and 746,52GB). This information is plain wrong, since the drive, when used in the USB enclosure, works as a single NTFS partition (2794,52GB). How come it’s shown as 3 partitions without filesystem when connected through SATA?!

Is Seagate using some proprietary way of storing the data when using the drive in its provided USB 3.0 enclosure? I didn’t use any kind of encryption. I just plugged the drive with USB 3.0 and started using it straight away, since it apparently came pre-formatted with an NTFS filesystem.

OMA

Posted 2015-10-12T00:21:21.597

Reputation: 1 221

The enclosure is probably doing 512e to 4Kn conversion for compatibility with Windows XP systems, which is causing the partition table to show up weird.

– bwDraco – 2015-10-12T01:29:57.457

It's a partition table issue caused by the absence of the enclosure's conversion to 4Kn. http://goughlui.com/2013/10/02/experiment-usb-to-sata-bridge-chips-and-2tb-drives/

– bwDraco – 2015-10-12T02:02:29.607

Answers

The enclosure exposes the drive to the computer as an Advanced Format 4Kn device, allowing the use of MBR for compatibility with Windows XP systems. When the drive is removed from the enclosure, the change in logical sector format results in an invalid partition table.

External hard drives larger than 2 TiB in capacity often expose 4K sectors directly to the operating system. The 2 TiB limit commonly associated with MBR is tied to the traditional 512-byte sector size; 4K sectors are eight times as large and therefore extend the MBR limit to 16 TiB. This allows the use of MBR on disks larger than 2 TiB in capacity, enabling use on Windows XP and other systems which do not support GPT.
The underlying hard drive uses 512-byte sector emulation for compatibility with legacy systems. This means that while the disk physically has 4K sectors, the immediate host device (in this case, the enclosure) sees 512-byte sectors. However, to perform the aforementioned MBR expansion and enable Windows XP compatibility, the enclosure makes the drive appear to the computer as having 4K native sectors.
When the drive is removed from the enclosure, the 512-byte logical sectors of the underlying 512e disk are exposed. This results in an invalid partition table that cannot be correctly interpreted. The 746.52 GiB value you gave for the last "partition" when the drive is connected directly is precisely the amount of space that lies beyond the 2 TiB limit for MBR drives with 512-byte sectors.

More details about the implications of this conversion are available in this blog post.

bwDraco

Posted 2015-10-12T00:21:21.597

Reputation: 41 701

+1 Thank you for explaining this! Is there such a thing as a USB enclosure that does not do this? – JakeGould – 2015-10-12T01:49:14.493

My Thermaltake BlacX dock, at least via eSATA, doesn't show my 512e 3 TB WD Green as 4Kn. – bwDraco – 2015-10-12T01:50:31.577

Thanks for your detailed explanation! I guess off-brand enclosures don't usually do this, don't they? I got an "Intenso" enclosure which (AFAIK) doesn't do this (it included a 2TB Seagate hard drive when bought). BTW, I've added my motherboard model to the original post just in case it's useful. – OMA – 2015-10-12T12:13:48.413

1By default all USB enclosures don't do this, ones that do (such as the above, bundled with a specific drive) are the exception. – qasdfdsaq – 2015-10-12T13:04:44.203

1@OMA Generic enclosures don’t behave that way since they are made for do-it-yourself folks who would know to check the specs and not need some weird things happening for Windows XP to work. The enclosures that drive manufacturers like Seagate and Toshiba make are designed this way to make their drives more appealing to average non-tech users who have no idea that they can even open their enclosure to get a bare hard drive out of it. So in the long run for someone like you it might be worth it to find a generic USB enclosure that can handle drives larger than 2TB in size. – JakeGould – 2015-10-12T17:58:15.157

I wasn't talking about empty enclosures. Of course those don't mess with the hard drive sectors. I was talking about other external hard drives. – OMA – 2015-10-12T18:36:31.850

Anyway, what would be the steps to take to properly use the drive outside the Seagate Backup Plus enclosure? Just re-partition and re-format it while plugged to my computer as a SATA drive and then copy everything over again? Is that enough or do I need to do anything extra to avoid any performance penalties when using this AFD drive? – OMA – 2015-10-12T19:02:38.787

@OMA: If you'd like to just reuse the underlying drive (and any existing data is backed up or no longer needed), that's okay. Windows 7 knows how to properly set up Advanced Format drives for optimal performance. – bwDraco – 2015-10-12T19:47:27.617

@OMA If you just want to reformat the drive for use inside a machine, that’s not an issue. Just reformat it and that’s it. But—like my answer describes—some people use external enclosures to transfer data and then remove the drive to place into an machine internally for different reasons. If you want to retain the data that existed when it was external, then you simply can’t. But the drive itself is not magical in anyway. It’s just a drive you can use anywhere you want to. – JakeGould – 2015-10-12T23:11:55.277

By "simply can't" I take it that what you mean by this is that this translation being done may be proprietary/not-standard/rare and that an appropriate driver doesn't exist? I am now only able to continue to use my newly liberated Seagate drive with the original USB3 board. This is annoying because I still can't mount it inside my desktop because of the extra length of this adapter board. So at some point I have to copy data off of it and place it back onto it after reformatting it. – Steven Lu – 2016-02-21T17:17:40.857

It says the drive has 3 partitions (349,31 GB of RAW data and two unassigned partitions of 1698,68 GB and 746,52 GB). This information is plain wrong, since the drive, when used in the USB enclosure, works as a single NTFS partition (2794,52 GB). How come it’s shown as 3 partitions without filesystem when connected through SATA?!

Is Seagate using some proprietary way of storing the data when using the drive in its provided USB 3.0 enclosure?

Two thoughts based on my personal experience:

In my experience, the old trick of copying data to an external SATA drive in an external USB enclosure and then using it without issue with an internal SATA connection doesn’t work with drives that are larger than 2TB in size.

Meaning the format the enclosure uses for data transfer is “oddball” or proprietary partitioning format that won’t allow a simple swap. Or maybe something else is happening? Perhaps it’s being formatted as RAID on a low level for some reason? Maybe even LVM? Don’t know since I never checked this out in depth.

Mind you this is not the case with all external SATA enclosures, but from my casual tests the manufacturer specific enclosures—such as ones from Toshiba and Seagate—a disk formatted in such an enclosure won’t be readable by the system if connected directly.
Unclear what motherboard you might be using, but not all SATA connections will allow for drives that are larger than 2TB in size. I would check your system specs to see if that might be the case.

JakeGould

Posted 2015-10-12T00:21:21.597

Reputation: 38 217