Borg works great. I used it at a shop that had lots of servers, but didn't have any real backups-other than when someone would remember to go swap external USB drives and hope they actually ran.

Set it up on a bunch of servers with a simple cron job, the initial backups went quickly, and the incrementals were really fast. Made great use of an old Dell server that wasn't doing anything else and had lots of slow disks in it.