I have backed up my Mac & two External drives using a third external drive & TM until a disc failure took one of my external drives out. I have installed a new external drive & retrieved the stuff that was on my original failed drive. I would like to include this new drive into my TM backup but I have no idea how to achieve this. I have considered renaming my new drive to that of the failed drive however I cannot believe that this will work because it seems such a simple process. I have replaced a WD My Book HD with a LaCie.