OpenWRTのRAID-1(ミラーリング)で運用していたディスクを取り外し、1台だけ別のシステム(具体的にはRaspberry Pi)に接続してマウントする。
一般的なLinuxシステムでも同じ方法でできるはず。

取り外したHDDを適当なHDDケースに入れて、RaspberryPiにUSB接続する。

そのときのdmesgの抜粋

[ 2072.532442] usb 2-2: new SuperSpeed USB device number 2 using xhci_hcd
[ 2072.553795] usb 2-2: New USB device found, idVendor=152d, idProduct=0578, bcdDevice=72.05
[ 2072.553817] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2072.553830] usb 2-2: Product: GW3.5AM-SU3P
[ 2072.553840] usb 2-2: Manufacturer: Kuroutoshikou
[ 2072.553850] usb 2-2: SerialNumber: 0C51800004CB
[ 2072.597970] scsi host0: uas
[ 2072.599259] scsi 0:0:0:0: Direct-Access     ST3000DM 007-1WY10G       7205 PQ: 0 ANSI: 6
[ 2072.633904] sd 0:0:0:0: [sda] 5860533168 512-byte logical blocks: (3.00 TB/2.73 TiB)
[ 2072.633920] sd 0:0:0:0: [sda] 4096-byte physical blocks
[ 2072.634133] sd 0:0:0:0: [sda] Write Protect is off
[ 2072.634139] sd 0:0:0:0: [sda] Mode Sense: 53 00 00 08
[ 2072.634476] sd 0:0:0:0: [sda] Disabling FUA
[ 2072.634482] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 2072.688163] sd 0:0:0:0: [sda] Preferred minimum I/O size 4096 bytes
[ 2072.688180] sd 0:0:0:0: [sda] Optimal transfer size 33553920 bytes not a multiple of preferred minimum block size (4096 bytes)
[ 2072.721168] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 2072.727956]  sda: sda1 sda2 sda3
[ 2072.728420] sd 0:0:0:0: [sda] Attached SCSI disk
hiroshi@omvpi:~ $ 

hiroshi@omvpi:~ $ sudo fdisk -l /dev/sda
Disk /dev/sda: 2.73 TiB, 3000592982016 bytes, 5860533168 sectors
Disk model: 007-1WY10G      
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: 36F7B8D6-ED67-4C9C-A0A9-51CD930408B4

Device       Start        End    Sectors  Size Type
/dev/sda1       64    8388671    8388608    4G Linux RAID
/dev/sda2  8388672    9437247    1048576  512M Linux RAID
/dev/sda3  9437248 5860529072 5851091825  2.7T Linux RAID
hiroshi@omvpi:~ $