For backups, I use rdiff-backup across 60G+ of user data, nightly. rdiff-backup uses librsync to transfer files, but also handles incremental backups and seems to be fairly efficient at storing increments. Nightly, maybe 10%, maximum, of the user data changes and backups complete in less than 2 hours. Load is low enough I could run several times a day if I needed.

Databases should be properly dumped to a file before back up.

I've also tried BackupPC, which was a great project, but probably not the best fit for this case. I was running it in a virtualized container, and I ran into a lot of memory issues backing up large servers. This issue likely came down to memory -- not necessarily BackupPC itself -- but I dropped it because backups commonly took around 6-8h, if they didn't silently hang on me.