I just added a new cache drive (1TB).  My plan is to remove the second drive (240GB) and then replace it with another 1TB drive and then mirror it.  I added the new cache and have pointed all shares at it as needed.  I have read dozens of posts about doing this but everyone seems to be slightly different - either on an older version of Unraid or not quite my configuration.  As a result I will post my details and hope I can get specific information on how to do this in my case as I don't want to