Guy, all you need to do is pull the bad drive and insert a replacement. First thing to try is popping it out then back in. If it's bad, it will flash red agin after a few minutes. If it's good, it will go yellow to tell you it's rebuilding. Sometimes if the DROBO gets bumped a drive will jostle just enough to appear scrambled when in fact nothing is wrong, why I recommend the popping out and back in. I had this happen a few times with Samsung drives, but never Seagates or WD's. You do not need to take the DROBO offline to do this --- jut pop the bad drive, wait 30 seconds and pop it back in.