The following describes NSP cluster redundancy rules.
At a single site, a master is elected among the cluster of three VMs. Between sites, a single cluster at one site is the primary/active site and the other DR site is the secondary/standby site.
The application processes at the standby site are shut down but the Neo4j and other databases are synchronized with the primary/active site.
Switching to the standby site can be initiated manually or by using an automated approach stemming from the loss of heartbeat between the primary and standby sites.
If the NSP cluster at the primary/active site is down (two out of three servers must be inactive, shut down, or failed), the heartbeat mechanism between the primary and standby NSP clusters fails after three timeouts. This initiates the active role at the secondary/standby site.
When the NSP cluster at the primary site is back up, the heartbeat mechanism between the primary/standby and secondary/active NSP clusters is restored. The primary site can be manually restored as the active site. Automatic reversion to the primary NSP cluster is not supported.