Snapshot Pro saturate the I/O Usage on server

Hi to all, when I try to do a site backup with Snapshot Pro and when the plugin start its process it saturate the I/O Usage in the server. The I/O Usage in the server is up to 1024 KB/s.
After some minutes the backup process end for some issues and I don't know what I should do to make the site backup.
Can anyone help me?