Default virtual machine settings control the order in which virtual machines are restarted (VM restart priority) and how VMware HA responds if hosts lose network connectivity with other hosts (host isolation response.)

These settings apply to all virtual machines in the cluster in the case of a host failure or isolation. You can also configure exceptions for specific virtual machines. See Customize VMware HA Behavior for an Individual Virtual Machine.

VM restart priority determines the relative order in which virtual machines are restarted after a host failure. Such virtual machines are restarted sequentially on new hosts, with the highest priority virtual machines first and continuing to those with lower priority until all virtual machines are restarted or no more cluster resources are available. If the number of hosts failures exceeds what admission control permits, the virtual machines with lower priority might not be restarted until more resources become available. Virtual machines are restarted on the failover host, if one is specified.

The values for this setting are: Disabled, Low, Medium (the default), and High. If you select Disabled, VMware HA is disabled for the virtual machine, which means that it is not restarted on other ESX/ESXi hosts if its ESX/ESXi host fails. The Disabled setting does not affect virtual machine monitoring, which means that if a virtual machine fails on a host that is functioning properly, that virtual machine is reset on that same host. You can change this setting for individual virtual machines.

The restart priority settings for virtual machines vary depending on user needs. VMware recommends that you assign higher restart priority to the virtual machines that provide the most important services.

For example, in the case of a multitier application you might rank assignments according to functions hosted on the virtual machines.

High. Database servers that will provide data for applications.

Medium. Application servers that consume data in the database and provide results on web pages.

Low. Web servers that receive user requests, pass queries to application servers, and return results to users.

Host isolation response determines what happens when a host in a VMware HA cluster loses its management network connections but continues to run. Host isolation responses require that Host Monitoring Status is enabled. If Host Monitoring Status is disabled, host isolation responses are also suspended. A host determines that it is isolated when it stops receiving heartbeats from all other hosts and it is unable to ping its isolation addresses. When this occurs, the host executes its isolation response. The responses are: Leave powered on, Power off, and Shut down (the default). You can customize this property for individual virtual machines.

To use the Shut down VM setting, you must install VMware Tools in the guest operating system of the virtual machine. Shutting down the virtual machine provides the advantage of preserving its state. Shutting down is better than powering off the virtual machine, which does not flush most recent changes to disk or commit transactions. Virtual machines that are shut down will take longer to fail over while the shutdown completes. Virtual Machines that have not shut down in 300 seconds, or the time specified in the advanced attribute das.isolationshutdowntimeout seconds, are powered off.

Note

After you create a VMware HA cluster, you can override the default cluster settings for Restart Priority and Isolation Response for specific virtual machines. Such overrides are useful for virtual machines that are used for special tasks. For example, virtual machines that provide infrastructure services like DNS or DHCP might need to be powered on before other virtual machines in the cluster.