You should RAID 1 your data drives and have backups. Redundant arrays and backups are two different things of course. You can partitian the 2tb drive in half and then setup a RAID 1 with that half and the 1tb drive. That way you will have two current copies of data in case either drive fails, plus your last backup and any other you have saved. Data dependibilty. If having a current second copy for fail-over at all times is not important and it is ok to lose anything since last backup then you won't need to setup a RAID 1.