Can you use Time Machine to shuttle data via a USB stick? How well does it work when you have more than two drives that you want to keep mostly synchronized?
It's not for snapshotting or mirroring. I used to use CarbonCopyCloner to clone my boot drive to an external USB drive every morning at ~4am, so if the internal drive on my iMac died I had an immediate bootable replacement.
(And when the internal drive DID die, I just rebooted the machine and took nearly a year to get around to replacing the internal drive!)