So I want a way to back up my data but I want the backup to be very light and portable and also fault-tolerant of a drive failure. In another thread I was going to drop $630 for a RAID enclosure with four 2.5" drives. Would it be possibly to do this via software and two external USB drives? Get two USB 3.0 enclosures, install a 2.5" drive in each, and plug them in simultaneously into two USB ports. And when I drag data, delete data, or modify data on one drive, the software automatically syncs all the changes on the other drive. This would be the lightest, most portable method. And no need for a power brick to power a 4-bay enclosure.