Evidian SafeKit is a clustering software with load balancing, real-time replication and automatic failover (free trial available here). It is compared in this article with hardware clustering solutions (shared disk clusters and load balancers).
Simplicity of a clustering software vs a hardware clustering
|SafeKit clustering software to build a software cluster||Hardware clustering to build a shared disk cluster||Hardware load balancing to build a farm cluster|
|Application clustering software on standard Windows or Linux servers||Hardware clustering of large database on a replicated mirror SAN||Network load balancing of large web portals|
Here are some examples of mirror application modules:
Here are some examples of farm application modules: