How is the capacity managed when placing instances in fault domains?

The correct answer involves understanding how instances are allocated within fault domains to enhance reliability and fault tolerance. Capacity management when placing instances is crucial for ensuring that resources are utilized effectively while also mitigating the risk of failures impacting service availability.

When instances are dispersed in a best-effort manner according to available capacity, it means that the system will attempt to distribute instances across different fault domains—such as servers, racks, or even data centers—while taking into account the current resource availability. This approach helps balance the load across the infrastructure and minimizes the potential impact of a single point of failure. By spreading instances, the system ensures that not all instances are concentrated in one area, thereby enhancing redundancy and resilience.

The other options do not accurately reflect the way instances are managed in relation to fault domains. For instance, distributing instances evenly without concern for capacity could lead to resource contention or exhaustion in specific areas. Similarly, placing instances based on highest demand might create a situation where certain fault domains become overloaded while others remain underutilized, which could compromise availability. Lastly, relying solely on manual selection by the user may introduce human error and inefficiencies in resource allocation, especially in large-scale environments where automation and intelligent distribution are preferred.

Thus, the best approach is to utilize