If the drive dies for some reason, you would contact our support group to arrange a replacement drive. Once you get the drive, you would power off the unit of course, then remove the failed drive, insert the new drive into the system. You would then power the Duo back up. At that point, the firmware on the unit would recognize the new drive, then go into what is called a RAID rebuild mode. It would begin rebuilding the drive array so that the contents of the second drive would be mirrored back into the new drive.
Hope that helps explain it.
