My understanding is that there are only 2 enVision solutions offered at this time. A single appliance solution and a multiple appliance series.
The multiple appliance series solution distributes portions of the application across multiple servers and offers some additional hardware failover redundency but does not address log data redundency.
The single appliance solution is a standalone all application services on one server. Additional high availability of data can be addressed through implementing 2 standalone appliances and sending source device logs to both servers. If one server is unavailable for some reason the other appliance is still receiving the data hence no loss of information. When the lost server is recovered you could always export the log data and load into the recovered server to put the two back in approximately the same state. Of course this doubles the network traffic so you will have to assess the impact to the organisation.
As always discuss options with RSA.