Solved RAID 1 - 2tb and 640gb Tags: NAS / RAID Caviar Storage Last response: July 3, 2012 12:01 AM in Storage Share sirgogo June 26, 2012 6:09:52 AM Hi all, I've never used RAID before, but I was interested in RAID 1. I have two drives: Drive A - 640 gb Caviar Black Drive B - 2 tb Caviar Green What I want to do is create a backup (RAID1) of my Drive A onto my Drive B, and use the remaining space as a data partition. So I want 3 partitions: A - Drive A - 640 gb (Primary) B - Drive B - 640 gb (Backup) C - Drive B - 1408 gb (Misc data) Is this possible? More about : raid 2tb 640gb Best solution Dereck47 a c 545 G Storage June 26, 2012 11:06:11 AM No. This is how you calculate the size of a RAID-1 array: Storage Efficiency: 50% if drives of the same size are used, otherwise (Size of Smaller Drive / (Size of Smaller Drive + Size of Larger Drive) ) said:Storage Efficiency: 50% if drives of the same size are used, otherwise (Size of Smaller Drive / (Size of Smaller Drive + Size of Larger Drive) ) So the total size of your RAID-1 array with those 2 drives would be 633.6GB. Your drives need to be equal size for maximum storage efficiency. Share sirgogo July 3, 2012 12:01:47 AM Best answer selected by sirgogo. m 0 l Can't find your answer ? Ask ! Publish Read discussions in other Storage categories Hard Drives DVD Drives DVD Writers Optical Media Flash Media NAS/RAID SSD Western Digital !