How can you ensure high availability for ArcGIS Server?

High availability for ArcGIS Server is best achieved by implementing a load balancer along with a multi-server setup. This design allows for redundancy and improves reliability, as multiple servers can share the workload. In a multi-server environment, if one server goes down, the load balancer can redirect requests to the remaining operational servers, minimizing downtime and ensuring that services remain available to users. This setup not only enhances performance during peak times but also provides a failover option, contributing to a robust infrastructure that can handle unexpected disruptions.

In contrast, the other options do not adequately address the need for high availability. Relying on a single large server creates a single point of failure; if that server goes down, all services become unavailable. Limiting user access does not inherently contribute to availability; rather, it may restrict legitimate users from accessing necessary services. Creating offline copies of services can be useful for backup or disaster recovery, but it does not ensure continual access or service availability for live users. Hence, a multi-server approach with load balancing remains the most effective method for achieving high availability in ArcGIS Server environments.