Figure 2 represents a better hardware scheme, using well-designed application software to enhance availability. If the coin counter misses an acknowledgement, it resends. If the data collector misses an acknowledgement, it logs an error on the alarm console and resends. It uses the fastest Digital Alpha processors available and an external, self-contained RAID subsystem connected to a shared ultra SCSI bus. With clustering technology, the client does not need to know.
Clusters advertise services using a cluster alias name.
Client applications connect to the alias name, offered by whichever physical server is primary for that application. Memory leaks, conflicts among competing DLLs, hangs, and general bugginess are too common. They have no concept of a cluster, which will contain more than one physical server. Although popular 4GL GUI tools might be fine for certain applications, we cannot depend on such tools to run the casino. Most of these tools fill the screen with ugly error messages when they encounter a problem and leave it to the user to sort it all out.