Why is it important for ESXi to manage idle memory effectively in vSphere 6?

Managing idle memory effectively is crucial for ESXi in vSphere 6 primarily because it directly impacts the performance of active virtual machines. When ESXi can efficiently manage memory resources, it ensures that available memory is allocated to virtual machines that are currently active and demanding resources. This minimizes latency and maximizes throughput, allowing those VMs to function at optimal levels.

High performance for active virtual machines is essential in a virtualized environment where workloads can be dynamic, meaning that memory needs can change rapidly based on the workload. Effective memory management allows the hypervisor to quickly react to these changes, providing additional memory resources to VMs that are busy, thereby maintaining performance levels and preventing slowdowns that can occur when memory resources are inadequately allocated.

While other options also hold some relevance in virtualization management, the primary goal of effective idle memory management is to ensure that the active workloads run as efficiently and quickly as possible, which makes option A the most important reason.