Our back-up is taking 3-4 Gb per day... Why and how to solve it?

Hello gentlemen,

I hope you can help me because this is a very serious that I can't wait to resolve... Our back-up is currently taking 3 up to 4 Gb per day and we don't know why. We had 270 Gb yesterday and we are today at 274.3 Gb. We keep a computer history of the messages for only 50 days. Here is a picture of what's currently taking the most data place in our healtshare system:

(don't forget that our DB is also connected to the back-up, maybe it is related, I don't know)

Thanks you in advance,

Thomas