WDMyCloud 4TB NAS OS5 Inaccessible after power outage - flashes blue then red

Perhaps try this, it should work on any Linux based NAS. Follow the link for complete detail.

Resolution

Recover data using a PC

  1. Make sure your PC has sufficient drive slots for drive installation.
  2. Remove the drives from your Synology NAS and install them in your PC. For RAID or SHR configurations, you must install all the drives (excluding hot spare drives) in your PC at the same time.
  3. Prepare an Ubuntu environment by following the instructions in this tutorial.
  4. Go to the Files on the left bar and select Home.
  5. Right-click and select New Folder, and create one or more folders as mount points for accessing data.1
  6. Right-click on the new folder(s), click Properties, the parent folder with folder name is ${mount_point}.
  • Example: If the parent folder is /home/ubuntu/ and the folder name is Test, the mount point will be /home/ubuntu/Test/
  1. Go to Show Application in the lower-left corner > Type to search….
  2. Enter Terminal in the search bar and select Terminal.
  3. Enter the following command to obtain the root privileges.

sudo -i

  1. Enter the following commands to install mdadm and lvm2, both of which are RAID management tools. lvm2 must be installed or vgchange will not work.

apt-get update apt-get install -y mdadm lvm2