Run mdadm - this command is used to manage and monitor software RAID devices in linux.
mdadm --detail /dev/md0 or
mount -t ext4 /dev/md0 /share/MD0_DATA
mdadm --examine /dev/sdd3
Add disk back to raid that is "removed"
mdadm --manage /dev/md0 --add /dev/sdd3
After this you should see your raid start to rebuild again.
If that doesn't work check to see if the RAID is online
1 – Download the file to NAS:
2 – Apply execute permission:
chmod +x md_checker
3 – Run the script:
II – Fixing RAID With Usign AFR Command (Safe Way)
If your RAID structure seems “Not Active” and cannt access your files, you can fix this by this way;
Warning; if you’re not sure, don’t do it yourself, contact qnap support!
so we type this command line to fix our RAID;
mdadm -AfR /dev/md0 /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3
What if we got “missing” or “Rebuildin” HDD? you must fallow right order & dont add “Missing” HDD’s to this command line
1 – Type This command to get RAID back online again;
mdadm -AfR /dev/md0 /dev/sdg3 /dev/sdh3 /dev/sda3 /dev/sdf3 /dev/sdc3 /dev/sdd3 /dev/sdb3
2 – And Now RAID Becomes Active Again!
3 – To mount RAID back again;
4 – Now RAID Comes back, and rebuilding start!