Originally Posted by
Tannin
[b]using two external USB 3 x 2 Tb drives[/b
External drives are still the best: by far the cheapest, and generally the most reliable - provided, of course, that you have multiple units.
of which I manually sync once a day
Ouch! This is way, way too often. Very dangerous. Many data threats take a long time to become obvious. Suppose you have one of those data-encryption infections (which are very common now). What you need is an OLD backup, pre-infection. Aim to have a year-old backup, one a month or two old, and a recent one. Old backups are precious in many ways and can protect you against a number of different threats, including your own stupidity. (Are you stupid? Well, do you own a computer? Yes? Then you've done something stupid! Chances are, you will do some other stupid thing soon enough. We all do. It goes with the territory. Good backups are the only defence.)
I used to have a off site storage (internet) too but with 1.5 Tb of data this can become hard to achieve.
Yes. It gets very expensive. Plus your provider may not be around when you need them. Plus they read your data and sell it. (Read the fine print!)
I am about to upgrade my external storage looking to something more along the lines of Mirrored / RAID storage, possible hot swap.
Don't even think about it. Can of worms.
Your best answer, by far, is simply to buy more external drives. Plenty more! No such thing as too many backups.