Here at my company we have three Hudson CI servers with 100+ jobs configured. We are looking for an automated way to periodically backup job configurations and
I am using thinbackup, which supports full backup and differential backup, and you could schedule when it runs the backup using cron job like syntax. It only backups the critical configurations so it doesn't take much spaces.
See more details at: https://wiki.jenkins-ci.org/display/JENKINS/thinBackup