In previous Oracle MICROS POS products, solutions such as Double Take and Legato provided fault tolerance if the application server failed. These products are not supported for use with Simphony. Instead, you can use network clustering and load balancing to achieve a degree of resiliency through redundancy, in addition to their primary function of improved throughput. There are two primary means to implement this solution.
The Microsoft Windows Server software contains a feature called Network Load Balancing (NLB) which may be used to cluster the application servers together. This option does not require any additional licensing costs.
Hardware solutions can also be used to handle this functionality. These solutions are more expensive than implementing the Microsoft Windows based solution, but can provide a higher degree of flexibility and configuration options.
Network load balancing detects server failure and balances the load on the remaining configured application servers. Network load balancing does not detect failure of services (including IIS).