According to my Control Panel my site was using 183 MB of space. I did a backup using the module. After a couple of hours wait I FTP'd my site and couldn't find the tarball anywhere in the page, so I backed up again. Nothing happened. So I went to my control panel to see if the tarball was hidden somewhere. What I found is that I was using now 667MB of hard drive space, almost my limit, but the tarballs don't show anywhere. Not in the visible nor in the invisible directories.
I must mention that I am a happy user of the version5 backup module, and this is the first time I try it in a 4.7 installation. In version 5 the only problem I have is the blank page also documented as an issue, but I don't really care. the tarball is always there