[dnanian]

Dewey:

In general, it's not practical -- from a restoration standpoint -- to back up four to one volume. How would you properly restore it?

So, you've got a few choices.

First, you can partition the external drive appropriately. I think this is your best course of action: partition into appropriate sizes, and leave the remainder in its own partition for other storage.

You can also create a two partitions, one for the boot volume and another for data, then store sparse images (as described in the FAQ) for the other three volumes. This simplifies the partitioning, and still gives you a bootable main drive backup... but I'd avoid too many sparse images if you don't have to have them.

Finally, you can go with all sparse images. No direct boot, but the most "disk space" flexibility.

In general, disk space is cheap. So, I'd use the first technique.