I purchased CCC for my Macs and it worked an absolute treat for the two years I ran it.
Now, I have an external LaCie ThunderBolt drive with 3Tb of space after setting up a RAID1 array. I keep iTunes movies/TV Shows, handy software apps, larger personal files and also all of my business related files on the drive.
This drive is cloned on a weekly basis to two separate USB drives. One of which is 3Tb (kept off-site), the other is a WD Passport with 2Tb of free space (kept in a laptop bag so I have full access to everything on the road).
As I currently only use 1.4Tb this isn't much of a problem although I do need an app that can clone to drives with a smaller capacity. In time I would remove a certain folder from the clone if need be, CCC offered that option.
I don't mind if I need to purchase something, so long as I don't need to reboot the computer in order to perform the operation. None of the drives are bootable, so its just moving regular files from one place to another and keeping all the drives in sync.
I hope that explains what I am looking for and there is something out there suited to my needs. I can't keep copy/pasting folders much longer as I need to delete the full folder and recopy to ensure it is all up-to-date.
Thanks in advance.