Something to ass, since no one mentioned it. All of the drives have to have the same size partition on different physical disks to create a RAID5 drive. So, if you have 4 drives that each are 7GB, 5GB, 10GB, and 7GB, and you wanted to use all of the drives, then you would create a 5GB partition on the other larger drives to create about a 14GB RAID5 drive. RAID5 uses 1/3 or that equivelant to 1 of the partitions of the RAID set of the total disk space for parity information.