Hello Will-
Thanks for your interest in Total Upkeep for backing up your clients’ websites.
Total Upkeep does store backups on the local server, but it can be configured to remove them as soon as they’ve been uploaded to the remote location so that the disk space is freed as soon as the process is done.
In its current form, Total Upkeep does not use “incremental” backups, where only small changes to the site are backed up. Each backup file is designed to be a self-contained recovery for the full site that can not only be used to restore the site in the event of an error, but to be a portable copy of the site for transferring to another host or a local development environment.
We are currently investigating implementing an incremental backups feature, but that is a ways down the feature roadmap right now, and I can’t say how soon that feature might be released.