Note: These steps are for DSM 6

How Synology Support repairs RAID

1. Backup your data first!

2. Run cat /proc/mdstat to check what your device names are: /dev/md# and /dev/sda# or /dev/sata# or /dev/nvme#

3. Run the following commands:

   sudo synospace --stop-all-spaces

   sudo syno_poweroff_task -d

   sudo mdadm -Sf /dev/md4 # Replace md4 with correct md number

   sudo mdadm -AfR /dev/md4 /dev/nvme2 # Replace md4 with correct md number and nvme2 with correct nvme number