I have a RAID 1 mirror on a Lacie 2 Big USB3. When I break the mirror by pulling out one drive, keep making changes on the remaining drive and finally put the first one back in, the drives stay happily out of sync. The unit doesn't seem to detect the mirror was broken. The manual only explains the steps to take to replace a failed drive with a new drive. Does it only re-mirror if the replacement drive is new? What does it look at to determine that?