How to mount a RAID 1 volume from a Seagate Blackarmor NAS

A step-by-step guide on how I got my data back

Posted on June 13, 2016

WARNING: Please note that this article describes my experience and the results you might get reproducing what I did will surely be different. Please understand that I am not responsible for the results you might get reproducing what I did. If you choose to follow my notes and anything bad happens, don't blame me, you are responsible for what you do. In doubt, my advice is to go and read some news on

This is a step-by-step guide on how I got back access to the data stored in a RAID 1 volume created on a Seagate Blackarmor NAS.

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The content of this tutorial is based on other posts:

The process was done using a GNU/Linux computer (a Raspberry Pi in my case) and an external USB powered connector to connect the disk to the Raspberry Pi.

I had four disks inside the NAS, organized in two RAID 1 volumes: disks one and two for first RAID 1 volume, disks three and four for the second RAID 1 volume.

As first thing I prepared the Raspberry Pi, making sure it had mdadm and lvm2 installed, the dm-mod kernel module loaded, and the directories for the mount points:

sudo apt-get update
sudo apt-get install mdadm
sudo apt-get install lvm2
sudo modprobe dm-mod
sudo mkdir -p /mnt/seagate/raid/v1/
sudo mkdir -p /mnt/seagate/raid/v2/
sudo mkdir -p /mnt/seagate/raid/v3/
sudo mkdir -p /mnt/seagate/raid/v4/

mdadm is a RAID management tool, lvm is a logical volume management tool, dm-modis the device mapper module.

As soon as I took the disks out of the NAS I applied a label on them to be able to identify the position they had in the NAS.

After attaching one of the disks to the computer, the `dmesg` command gave me the following:

[ 2228.677193] usb 1-1.3: new high-speed USB device number 4 using dwc_otg
[ 2228.778427] usb 1-1.3: New USB device found, idVendor=152d, idProduct=2338
[ 2228.778448] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=5
[ 2228.778462] usb 1-1.3: Product: USB to ATA/ATAPI bridge
[ 2228.778474] usb 1-1.3: Manufacturer: JMicron
[ 2228.778486] usb 1-1.3: SerialNumber: 000000000000
[ 2228.779883] usb-storage 1-1.3:1.0: USB Mass Storage device detected
[ 2228.782849] scsi host0: usb-storage 1-1.3:1.0
[ 2229.778109] scsi 0:0:0:0: Direct-Access ST3000DM  001-1CH166  PQ: 0 ANSI: 5
[ 2229.779566] sd 0:0:0:0: [sda] Very big device. Trying to use READ CAPACITY(16).
[ 2229.779851] sd 0:0:0:0: [sda] 5860533168 512-byte logical blocks: (3.00 TB/2.73 TiB)
[ 2229.780726] sd 0:0:0:0: [sda] Write Protect is off
[ 2229.780750] sd 0:0:0:0: [sda] Mode Sense: 28 00 00 00
[ 2229.781221] sd 0:0:0:0: [sda] No Caching mode page found
[ 2229.781240] sd 0:0:0:0: [sda] Assuming drive cache: write through
[ 2229.782469] sd 0:0:0:0: [sda] Very big device. Trying to use READ CAPACITY(16).
[ 2229.790022] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 2229.859446]  sda: sda1 sda2 sda3 sda4
[ 2229.861563] sd 0:0:0:0: [sda] Very big device. Trying to use READ CAPACITY(16).
[ 2229.862595] sd 0:0:0:0: [sda] Attached SCSI disk

As you can see from the "[ 2229.859446] sda: sda1 sda2 sda3 sda4" line, the device /dev/sda has 4 partitions. Using fdisk to get more info out of the partition table:

Disk /dev/sda: 2.7 TiB, 3000592982016 bytes, 5860533168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 16B85A47-8C17-4052-A96B-2741CCB346FB

Device       Start        End    Sectors    Size Type
/dev/sda1   195312    2283203    2087892 1019.5M Linux RAID
/dev/sda2  2283204    4373046    2089843 1020.4M Linux RAID
/dev/sda3  4373047    5416015    1042969  509.3M Linux RAID
/dev/sda4  5416016 5860517599 5855101584    2.7T Linux RAID

This is what I god trying to mount the biggest partition, the /dev/sda4:

$ sudo mount /dev/sda4 /mnt/seagate/raid/v3/
mount: unknown filesystem type 'linux_raid_member'

To get more info about the RAID level I used mdadm to examine the /dev/sda4 partition running sudo mdadm --examine /dev/sda4

$ sudo mdadm --examine /dev/sda4

Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : 1d121553:6712f248:d49a9aaa:31df2e71
Name : 4
Creation Time : Mon Sep 23 01:53:40 2013
Raid Level : raid1
Raid Devices : 2

Avail Dev Size : 5855101312 (2791.93 GiB 2997.81 GB)
Array Size : 2927550656 (2791.93 GiB 2997.81 GB)
Data Offset : 272 sectors
Super Offset : 8 sectors
Unused Space : before=192 sectors, after=0 sectors
State : clean
Device UUID : 2d7348a4:bfd0d282:c25de601:e94cca43

Update Time : Sun May 15 11:06:53 2016
Checksum : 307a2445 - correct
Events : 991

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

Then I used mdadm again to create the virtual md device, used to mount the logical volume:

$ sudo mdadm -A -R /dev/md9 /dev/sda4
mdadm: /dev/md9 has been started with 1 drive (out of 2).

Running fdisk /dev/md9 I could see clearly that the device contains a logical volume:

Welcome to fdisk (util-linux 2.25.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

/dev/md9: device contains a valid 'LVM2_member' signature, it's strongly recommended to wipe the device by command wipefs(8) if this setup is unexpected to avoid possible collisions.

Device does not contain a recognized partition table.
The size of this disk is 2.7 TiB (2997811871744 bytes). DOS partition table format can not be used on drives for volumes larger than 4294966784 bytes for 512-byte sectors. Use GUID partition table format (GPT).

Created a new DOS disklabel with disk identifier 0x2af87d64.

Command (m for help): q

As next step I used lvm to activate the logical volume. First I used the vgscan tool to scan for available volume groups:

$ sudo vgscan
Reading all physical volumes.  This may take a while...
Found volume group "vg1" using metadata type lvm2

In my case the application showed me the existence of one volume group called vg1. The name of the group is needed by the vgchange tool to activate the volume:

$ sudo vgchange -ay vg1
1 logical volume(s) in volume group "vg1" now active

Clearly, the vg1 is now active. The lvs command gives more information:

$ sudo lvs
LV   VG   Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
lv1  vg1  -wi-a----- 2.73t

At this point I had a new device, /dev/vg1/lv1, which I used to mount the partition:

sudo mount /dev/vg1/lv1 /mnt/seagate/raid/v3/ -o ro,user

The mount command gave me positive feedback on the mounted drive:

/dev/mapper/vg1-lv1 on /mnt/seagate/raid/v3 type ext3 (ro,nosuid,nodev,noexec,relatime,data=ordered,user)

To unmount the device I used the following commands:

$ sudo umount /mnt/seagate/raid/v3
$ sudo mdadm -S /dev/md9


Using mdadm

sudo apt-get install mdadm
sudo apt-get install lvm2
sudo modprobe dm-mod
sudo mdadm -A -R /dev/md9 /dev/sda4
sudo vgchange -ay vg1
sudo mount /dev/vg1/lv1 /mnt/seagate/raid/v3/ -o ro,user

Using vgscan

sudo mdadm --examine /dev/sda4

From the command above read the "Data Offset" (in my case was "272" sectors) and use the value in the losetup command.

sudo apt-get install lvm2
sudo losetup --find --show --read-only --offset $((272*512)) /dev/sda4
sudo vgscan
sudo vgchange -ay vg1
sudo mount /dev/vg1/lv1 /mnt/seagate/raid/v3/ -o ro,user