As a bare minimum you need to backup configuration and data directories. They are located in /usr/local/percival/etc/lancelot-config and /usr/local/perciva/var/lancelot-data. Since the Percival keeps both configuration and data in files there is no need to in any special agent. Backup can be done with standard Unix tools like tar, cpio, or dump.
To perform a full rertore do: