My Book Backups

I just purchased a 4TB My Book Live Duo to serve as a new disk. I previously had a 4TB My Book Studio II setup as a RAID1 and it reached capacity.

I would like to use the Live Duo as the primary external hard drive and use the Studio II as it’s backup (both in a non-RAID setup).

I can’t see how to do this with Time Machine (yes, I’m on a Mac) or with the WD Anywhere Backup or WD Smartware.

Help!

You can use the safepoint feature of the my book 

http://wdc.custhelp.com/app/answers/detail/a_id/7570/session/L3RpbWUvMTMzMDM2OTY1OS9zaWQvZjVPdmxNUms%3D