Trying to access data from PMBR / GPT disk

Warner

10/21/23, 7:55 AM

I've taken an SSD from another (Windows/Linux dual boot) PC and I'm trying to access the data.

The problem is that GParted reports 'unallocated' and Ubuntu's "Disks" utitilies reports 'Unknown (PMBR)'.

Looking at the disk with fdisk shows me:

warner@x399-aorus:~$ sudo fdisk -l /dev/sda
Disk /dev/sda: 3.65 TiB, 4000787030016 bytes, 976754646 sectors
Disk model:                 
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 33550336 bytes
Disklabel type: dos
Disk identifier: 0xff10350b

Device     Boot Start        End    Sectors Size Id Type
/dev/sda1           1 4294967295 4294967295  16T ee GPT

While the same with gdisk gets:

warner@x399-aorus:~$ sudo gdisk -l /dev/sda
GPT fdisk (gdisk) version 1.0.5

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: not present

Creating new GPT entries in memory.
Disk /dev/sda: 976754646 sectors, 3.6 TiB
Model:                 
Sector size (logical/physical): 4096/4096 bytes
Disk identifier (GUID): C9D20369-5C0A-47BC-BF72-AC41F0EC07E5
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 5
First usable sector is 6, last usable sector is 976754640
Partitions will be aligned on 256-sector boundaries
Total free space is 976754635 sectors (3.6 TiB)

Number  Start (sector)    End (sector)  Size       Code  Name

And blkid is even less helpful:

warner@x399-aorus:~$ sudo blkid /dev/sda
/dev/sda: PTTYPE="PMBR"
warner@x399-aorus:~$ sudo blkid /dev/sda1

(blkid doesn't see any partition, gdisk doesn't see any partition or GPT, while fdisk sees sda1 with GPT)

I'm at a loss.. how do I proceed to get access to the data? Putting the disk back in a Windows OS just tells me it's a protected GPT and refuses to access the data.

1306

1 + 0

partitioning

mbr

gpt

Score:1

Ubuntu

Warner

10/21/23, 12:33 PM

Ok, so I'm not sure about the technical explanation, but I did find a solution: The disk was connected through a (Sabrent) USB-to-SATA connector. This connector has worked fine with previous SATA disks but seems to have caused a problem here.

Connecting the disk directly to SATA on the motherboard solved the issue.

+ 2

oldfred

10/21/23, 3:07 PM

There have been many reported issues with USB drive adapters. Some just do not work with large drives. Some are only powered by USB port which does not give enough power for a HDD but works ok for SSDs.

Rod Smith

2/15/24, 2:23 AM

Some external adapters convert blocks of eight 512-byte drive sectors into 4096-byte virtual sectors. You can see this in your `fdisk` and `gdisk` output, which report 4096-byte sectors. Since partitioning tools use sectors to define partition start and end points, changing the definition of a sector invalidates the partition table. In the case of GPT, it makes the partition table completely unreadable. Using an adapter that does *not* do this conversion would do no better, since you'd run into a 2TiB (2^32 sector) limit of USB. (That's why they do this conversion in the first place.)

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Trying to access data from PMBR / GPT disk

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