Hi,
I'm planning to implement ArcGIS Server Enterprise system with Redundancy and SQL clustering in virtual servers. The web adapter will also be installed in web server, the ArcGIS server will be installed in another server behind the firewall and the geodatabase will be installed in data server with SQL cluster. All duplicated through load balancer.
Is anyone has similar configuration in virtual server?
How many licenses of ArcGIS server I need?
As far as licensing, I'd talk to your rep.
On the technology side, take a look at: Deployment scenarios—ArcGIS Server (Windows) Installation Guide | ArcGIS Enterprise