"High-availability clusters (also known as HA clusters or failover clusters) are groups of computers (...) that can be reliably utilized with a minimum of down-time. They operate by using high availability software to harness redundant computers in groups or clusters that provide continued service when system components fail." (source: Wikipedia)
SMSEagle NXS-family of devices have built-in HA-cluster feature. 2 SMSEagle devices may be configured to work in a cluster, which will automatically detect faults and switch service between master-backup device. The following functions are monitored in HA-cluster:
- Apache2 WWW server
- PostgreSQL database
- SNMP agent
- Modem software (Gammu-SMSD daemon)
- Accessibility (response to ping) of whole node
Failover cluster is easily configured using web-GUI. See User's Manual, chapter "Failover (HA-cluster) feature" on detailed description of the feature.