Originally written late 2015
Recently, a drive failed in my software RAID 5 Array. These are the steps I found to take.
1st, remove the dying drive from the RAID.
Once the drives are removed from the RAID array, power down the server and replace the drive. Be certain that you are replacing the correct one. I used my drive's serial number to identify which one to remove.
Boot the server again, and login to a terminal. Now, the new drive should appear in the same /dev/sd* format as the previous drive. Now we copy the partition table from the other drives to the new drive.
Once that has completed, verify that the drives have appeared in the /dev directory.
Now just add the drive back to the RAID with the following mdadm command.