Dropbox is good but if you are looking for cost effectiveness or more space you can rely on Free CloudBacko according to my experience. I am using CloudBacko, it is not expensive. You can store as much TB you want to save maximum up to 100 TB of data storage. This is cost affective and free of charge up to 100 Tb. I found that my data is secured. I do not worry about leakage or any other error in restoring.