They will all need to be licensed for SQL Server, however with the pay as you go model you will be charged for licensing on a per second basis so if your DR VM is not always on then you won't be charged for licensing costs when this VM is not allocated.
I have a query regarding Pay as you Go SQL Server Licensing model for DR machines.
Sudhir Singh
1
Reputation point
We are planning to deploy 3 machines say A, B & C in IaaS deployment model.
A will host the production workload (Read+Write). On B & C we will configure the Read only replica using Always-on High availability.
B will host read only workload. C environment will be used only for DR purpose. We are not planning to do any query from this machine.
In this scenario for which machines we need to pay the SQL Server Licensing cost considering we do not have SQL Server Licenses and Software assurance.