Howtoforge posted a tutorial about using Openfiler 2.3 Active/Passive Cluster (Heartbeat, DRBD) with Offsite Replication Node

Openfiler is a Linux based NAS/SAN application which can deliver storage over nfs/smb/iscsi and ftp. It has a web interface over that you can control these services. The cluster we build will consist of two nodes replicating each other and taking over services and storage in case of emergency. Furthermore we have an Offsite Replication Server, which ideally stands in a physically different position and replicates the configurations/storage from which ever node is active. In case of emergency this Offsite Replication Server can be used to restore the cluster and to deliver the services.

  Openfiler 2.3 Active/Passive Cluster (heartbeat,DRBD) With Offsite Replication Node