Automating OpenDirectory Archiving and Backup
AFP548 has a great article and an example script to help automate the archiving of OpenDirectory.
Once you are automatically archiving the open directory settings. You can then easily configure automated backups of these files using a variety of backup utilities.
LBackup is a light weight open source backup utility, which supports network backup. In addition LBackup supports pre-run scripts, so the backup can take place and then the backup will start, provided the archiveing stage was successfull.
LBackup also supports email reporting, so you should be prompted to check what went wrong. Provided your mail services are still working.