Unable to Mount HDD Removed from NAS & Connected to Ubuntu via USB-SATA Adapter

Question

I am trying to access data from a 8TB HDD that is removed from a non-functining QNAP NAS device. The HDD is connected to an Ubuntu 20.04 machine using a USB3-SATA adapter.

When the HDD is connected to the computer, no new drive icon can be found on the desktop. So I attempted to mount it manually using the bash terminal. I have identified the HDD as /dev/sda by looking at dmesg and fdisk.

However, when I try to mount the HDD using

mount /dev/sda /media/exthdd

I get the error

NTFS signature is missing.
Failed to mount '/dev/sda': Invalid argument
The device '/dev/sda' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?

Tried Daniel B suggestion

mount /dev/sda3 /media/exthdd

and got the error

mount: /media/exthdd: unknown filesystem type 'linux_raid_member'.

Tried

mdadm --assemble --run /dev/md0 /dev/sda3

but got the error

mdadm: /dev/sda3 is busy - skipping

How can we access the data in this HDD? Thank you!

---

Part of dmesg:

[  127.845809] sd 4:0:0:0: [sda] Synchronizing SCSI cache
[  128.104836] sd 4:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_ERROR driverbyte=DRIVER_OK
[  142.769194] usb 10-3: new SuperSpeed Gen 1 USB device number 2 using xhci_hcd
[  142.789851] usb 10-3: New USB device found, idVendor=174c, idProduct=55aa, bcdDevice= 1.00
[  142.789854] usb 10-3: New USB device strings: Mfr=2, Product=3, SerialNumber=1
[  142.789855] usb 10-3: Product: ASM1156-PM
[  142.789856] usb 10-3: Manufacturer: ASMT
[  142.789857] usb 10-3: SerialNumber: 00000000000000000000
[  142.791213] scsi host4: uas
[  142.803693] scsi 4:0:0:0: Direct-Access     ASMT     ASM1156-PM       0    PQ: 0 ANSI: 6
[  142.820428] sd 4:0:0:0: Attached scsi generic sg0 type 0
[  142.837024] sd 4:0:0:0: [sda] 15628053168 512-byte logical blocks: (8.00 TB/7.28 TiB)
[  142.837026] sd 4:0:0:0: [sda] 4096-byte physical blocks
[  142.837151] sd 4:0:0:0: [sda] Write Protect is off
[  142.837153] sd 4:0:0:0: [sda] Mode Sense: 43 00 00 00
[  142.837361] sd 4:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[  142.841558] sd 4:0:0:0: [sda] Optimal transfer size 33553920 bytes not a multiple of physical block size (4096 bytes)
[  151.664442]  sda: sda1 sda2 sda3 sda4 sda5
[  151.774943] sd 4:0:0:0: [sda] Attached SCSI disk

sudo fdisk -l /dev/sda:

$ sudo fdisk -l /dev/sda
Disk /dev/sda: 7.28 TiB, 8001563222016 bytes, 15628053168 sectors
Disk model: ASM1156-PM      
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: D0220E114E88-4C1E-94C3-C96BBF594E88

Device           Start         End     Sectors   Size Type
/dev/sda1           40     1060289     1060250 517.7M Microsoft basic data
/dev/sda2      1060296     2120579     1060284 517.7M Microsoft basic data
/dev/sda3      2120584 15610264109 15608143526   7.3T Microsoft basic data
/dev/sda4  15610264112 15611324399     1060288 517.7M Microsoft basic data
/dev/sda5  15611324408 15628031999    16707592     8G Microsoft basic data

sudo mdadm --examine /dev/sda3:

/dev/sda3:
          Magic : a92b4efc
        Version : 1.0
    Feature Map : 0x0
     Array UUID : b20f5220:2d15d1c8:cca065c3:0d22eb1b
           Name : 2
  Creation Time : Tue Aug  1 00:52:21 2017
     Raid Level : raid1
   Raid Devices : 1

 Avail Dev Size : 15608143240 (7442.54 GiB 7991.37 GB)
     Array Size : 7804071616 (7442.54 GiB 7991.37 GB)
  Used Dev Size : 15608143232 (7442.54 GiB 7991.37 GB)
   Super Offset : 15608143504 sectors
   Unused Space : before=0 sectors, after=264 sectors
          State : clean
    Device UUID : f4754405:0ab328d5:623c86bd:xxxxxxxx

    Update Time : Fri Mar  5 10:20:54 2021
  Bad Block Log : 512 entries available at offset -8 sectors
       Checksum : 794bbf3a - correct
         Events : 68


   Device Role : Active device 0
   Array State : A ('A' == active, '.' == missing, 'R' == replacing)

cat /proc/mdstat:

Personalities : [raid1] 
md322 : active (read-only) raid1 dm-2[0]
      7235136 blocks super 1.0 [2/1] [U_]
      bitmap: 1/1 pages [4KB], 65536KB chunk

md2 : active (read-only) raid1 dm-1[0]
      7804071616 blocks super 1.0 [1/1] [U]
      
md256 : active (read-only) raid1 dm-0[0]
      530112 blocks super 1.0 [2/1] [U_]
      bitmap: 1/1 pages [4KB], 65536KB chunk

unused devices: <none>

sudo mdadm --detail /dev/md2:

/dev/md2:
           Version : 1.0
     Creation Time : Tue Aug  1 00:52:21 2017
        Raid Level : raid1
        Array Size : 7804071616 (7442.54 GiB 7991.37 GB)
     Used Dev Size : 7804071616 (7442.54 GiB 7991.37 GB)
      Raid Devices : 1
     Total Devices : 1
       Persistence : Superblock is persistent

       Update Time : Fri Mar  5 10:20:54 2021
             State : clean 
    Active Devices : 1
   Working Devices : 1
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : resync

              Name : 2
              UUID : b20f5220:2d15d1c8:cca065c3:xxxxxxxx
            Events : 68

    Number   Major   Minor   RaidDevice State
       0     253        1        0      active sync   /dev/dm-1

sudo mount /dev/dm-1 /media/exthdd:

mount: /media/exthdd: unknown filesystem type 'linux_raid_member'.

Answer 1

You identified the “filesystem” used as Linux Software RAID. The RAID arrays were already active, as indicated by /proc/mdstat.

To mount the contents, you’ll have to mount /dev/mdN where N is probably 2. There are two other RAID arrays (md256 and md322), corresponding to some of the other partitions, but those are unlikely to hold user data.

So do try mount /dev/md2 /media/exthdd. /dev/dm-1 is a member of the array, you wouldn’t use it directly.