How does the VCS VMwareDisks agent behave w.r.t its attribute ‘IsVMHAEnabled’?

The VMwareDisks agent enables vMotion and VMware Distributed Resource Scheduler (DRS) in VCS clusters that are configured in a VMware environment.
The agent behavior is influenced by the set of values that are assigned to its attributes. ‘IsVMHAEnabled’ is one of its attribute that defines whether or not the VMware vSphere HA is enabled. The attribute can take the following values:

  • 0 =  VMware vSphere HA is turned off
  • 1 =  VMware vSphere HA is enabled

The ‘IsVMHAEnabled’ attribute value must match the vSphere HA settings that are configured under VMware cluster settings.
The following table provides details about the VMwareDisks agent behavior w.r.t the value defined for ‘IsVMHAEnabled’ attribute and the corresponding vSphere HA settings:

vSphere HA setting

IsVMHAEnabled value

VMwareDisks agent behavior

0

0

The VMwareDisks agent considers that the VMware vSphere HA is turned off.

In the event of a failure the VMwareDisks agent immediately takes corrective actions to failover the service group to a target ESX host.

1

1

The VMwareDisks agent considers that the VMware vSphere HA is enabled.

In the event of a failure, the VMwareDisks agent waits for vSphere HA to start the failed virtual machine on a target ESX host.

The time for which VMwareDisks agent waits for vSphere HA to start the failed virtual machine is determined by the ‘VMRegisterWait’ attribute. The default is 120 seconds. Once the virtual machine is started, the VMwareDisks agent fails over the virtual disks. VCS then takes corrective actions to bring the service group online on a VCS cluster node.

 

A configuration having a mismatch between the vSphere HA settings and the value set for ‘IsVMHAEnabled’ is not supported.
If there is a mismatch between the vSphere HA settings and the value set for ‘IsVMHAEnabled’, the application service group failover operation may fail.
The following table provides details about the VMwareDisks agent behavior if there is a mismatch between the value defined for ‘IsVMHAEnabled’ attribute and the corresponding vSphere HA settings:

vSphere HA setting

IsVMHAEnabled value

VMwareDisks agent behavior

0

1

The VMwareDisks agent considers that the VMware vSphere HA is enabled.

In the event of a failure, the VMwareDisks agent waits for vSphere HA to start the failed virtual machine on a target ESX host.

Because the vSphere HA is set to 0, it does not fail over the virtual machine to a target ESX host and the VMwareDisks agent keeps waiting for vSphere HA to start the failed virtual machine on a target ESX host. As a result the application service group does not fail over.

1

0

The VMwareDisks agent considers that the VMware vSphere HA is turned off.

In the event of a failure the VMwareDisks agent immediately takes corrective actions to failover the service group to a target ESX host.

Because the vSphere HA is set to 1, there may be a conflict between the agent trying to failover the service group and the vSphere HA trying to failover the virtual machine on a target ESX host.

As a result the service group failover operation may fail with the following error:

VCS ERROR V-16-10061-22524 VMwareDisks:VMwareDisk_1Smiley Surprisednline:Failed to register VM to the current ESX host with error 'The specified key, name, or identifier already exists.’