RAID Rebuild should be automatic or you can to it manually from the My Cloud Main menu page in the RAID tab.
Go to andrep182 on how to expand RAID 1 drive size
- get to My Cloud main menu
- click on ‘storage’
- Under ‘Raid’ tab by ‘RAID Volume’, pick ‘Change RAID Mode’
- It’ll warn you that it’ll interrupt the current services. Press ‘continue’
- Pick RAID 1 and you should see ‘Expand Capacity’ option
