A Netmail Store storage cluster routinely replicates content objects to other nodes in the same cluster in order to improve fault tolerance and performance. For disaster recovery and other reasons, it may also be desirable to automatically replicate content objects to another, remote cluster. By remote cluster, we mean a Netmail Store cluster with the following properties:
- It has a different multicast domain.
- It is connected only via TCP transport.
- There may be one or more firewalls separating the two clusters.
- Message latency might be unpredictable.
- The two clusters may be unable to communicate at all for long periods of time.
The normal replication techniques used within a Netmail Store cluster, including the multicast-based bidding process and UDP-based internode communication, are not appropriate for remote replication between clusters of this sort. Therefore, a new mechanism is required. We call this Netmail Store Content Router.