We would like to know below details before proceeding with ArcGIS Enterprise Active- Active configuration on multi machine Deployment :
1. Whether ArcGIS Server requires 2 separate licenses for both machines to implement ArcGIS Enterprise HA Active- Active configuration?
2. Whether Portal for ArcGIS requires 2 separate licenses for both machines to implement ArcGIS Enterprise HA Active- Active configuration?
3. If this is the case to implement, our customer has 2 ArcGIS Server licenses but only 1 for Portal for ArcGIS.
4. Whether ESRI Customer service can help us to provide another portal for ArcGIS with free of cost to implement ArcGIS Enterprise HA Active- Active configuration?
I would put a request in to your distributor to find out. Having said that, this is what I have found because I'm looking at the same thing.
You will require a licence per ArcGIS server and you can use the same named user licence file for Portal as long as you don't exceed the total number of distinct named user count. Since this is HA config, the named users will be the same across the 2 servers hosting Portal. Esri Inc had confirm this for me about 6 months ago as I was looking into how to split the named users across multiple environments (eg. DEV, SIT, UAT & PRD) and they told me I didn't need split it as long the total count of distinct named users across all the environments didn't exceed the number of the named users that was provisioned.
Good luck with this