CrushFTP supports high availability mode for Enterprise licenses.
This mode will allow for multiple servers to have Session Replication between the servers. A client is valid on all servers, so if a load balancer directed the client to another server, their logged in session is still valid.
This can be combined with the ServerBeat feature to manage a Virtual IP between multiple machines. This way incoming access points to the VIP, and that VIP will move to a machine that is operational in the event the current machine using the VIP goes down.
Lastly the DMZ mode can be used placing a DMZ server being controlled by internal an CrushFTP server separated by a firewall allowing only outgoing initiated connections. There can be multiple DMZ servers controlled by one internal server, or multiple internal servers sharing in management of multiple DMZ servers.
There is no single point of failure related to the CrushFTP architecture in this High Availability mode.