I have a NAS on Ubuntu Server with 4 2TB hard drives in RAID 5. A couple of weeks ago, one of the hard drives died, but my RAID was working, although degraded. Luckily it was still under warranty and I was sent a new hard drive which I installed today. However, when trying to add the new hard drive into the RAID, it was not rebuilding. So I unplugged the hard drive and rebooted the machine. However, I accidentally set one of my OTHER hard drives in the RAID to fail and removed it using mdadm.
Now it says my RAID has two removed hard drives. I still have my 3rd hard drive with all my data still intact, but I don't know how to re-add it back into the RAID array, so it's back to a good (although degraded) state, so I can continue to add the 4th hard drive and rebuild the array. Is it possible to just have Ubuntu realize that the 3rd hard drive has my data and just have it recognized as part of the array again?
When I try to run:
sudo mdadm --manage /dev/md127 --re-add /dev/sdd1
mdadm: --re-add for /dev/sdd1 to dev/md127 is not possible
Please, any help that anyone can give would be much, much appreciated.