Once a host is determined to be isolated, we have the following three options:

• Disabled: Do not take any action, running VMs continue to run
• Shut down and restart VMs: The running virtual machines will be shut down (provided VMware tools are installed) and vSphere HA will restart the VMs on other hosts in the cluster
• Power off and restart VMs: The running virtual machine will be abruptly powered-off, vSphere HA will restart the VMs on other hosts in the cluster

The key question is when to choose what. The answer to this is subjective to certain conditions. If we know that the network is flaky, not highly redundant, or prone to intermittent outages, a host isolation perhaps is a common phenomenon. In such cases, it's best to leave this option disabled. As an evasive option as shutdown or restart can increase the outage time. On the other hand, if the network is known to be fairly stable and workloads are critical, its best to choose to shut down the VMs.

The choice between shutdown and power off are straightforward. For critical workloads it's best to save in-memory data through a graceful shutdown.