Yes HA do takes assistance from DRS sometimes before STARTING the failover of failed VM’s. If a cluster is configured with admission control policies and either “specify number of host failures cluster tolerates” or “percentage” based policy is used then sometimes it may happen that resources are not fully available on SINGLE host and is scattered throughout the cluster. In that case HA will WAIT before performing failover of VM’s and ask assistance of HA to defragment the resources.

Yes HA do takes assistance from DRS sometimes before starting the failover of failed VM’s. If a cluster is configured with admission control policies and either “specify number of host failures cluster tolerates” or “percentage” based policy is used then sometimes it may happen that resources are not fully available on single host and is scattered throughout the cluster. In that case HA will wait before performing failover of VM’s and ask assistance of HA to defragment the resources.