What is the minimum number of infrastructure controllers in a Cisco APIC cluster deployment for a production data center?

Cisco ACI APIC controllers for a production data center are typically deployed as physical appliances, not virtual ones, to provide dedicated resources and stability, making 'virtual appliances' incorrect.

Cisco ACI requires a minimum of three physical APIC controllers for a production deployment to ensure high availability and fault tolerance. This setup allows the cluster to operate even if one controller becomes unavailable, providing resilience for policy enforcement and fabric management.

Two physical APIC appliances do not provide sufficient redundancy for a production environment; a minimum of three is needed to maintain quorum and N-1 redundancy for critical operations.

Two virtual appliances is incorrect on both counts; it's an insufficient number for production redundancy and the form factor (virtual vs. physical) is not recommended for production.