vSphere Distributed Resource Scheduler (DRS) is probably the most underrated VMware technology. It is enabled/configured on a cluster of ESXi hosts. An ESXi cluster is a vCenter functionality that allows you to pool the compute resources (CPU and memory) from more than one ESXi host under a single manageable resource-umbrella. Compute resources are not contiguous beyond the physical boundaries of the hosts. Therefore pooling compute resources allow for the efficient placement of Virtual Machine workloads across ESXi hosts to ensure optimal resource utilization within the cluster.
During the lifecycle of the cluster, DRS periodically monitors the cluster's utilization and redistributes the VMs within the cluster. This is done to ensure that no single ESXi host in the cluster is overburdened with the resource demands of the VMs...
