Idea for particular HDD savings

Hello,

My problem is on my HDDs, last time my 2TB die however I lost all my files ... It is not the first time that I lost my HDD extern. So I use the guarantee and I buy an other one. My question is how to automate the files that I put on one disk to copy them on the other disk, in fact I don't want a ghost or a RAID (there is one disk inside my computer and the other outside) just a software or a windows tool. In fact it's like a RAID mirror without the combination of both.

One more thing I'm french and I use english forums because in my language nobody answers, so my english is bad, please don't remind me.