Information Technology Reference
In-Depth Information
After vSphere HA is enabled, you may occasionally need to temporarily halt it, such as dur-
ing network maintenance windows. Previously we discussed the behavior of vSphere HA when
a network partition or network isolation occurs. If you will be performing network maintenance
that might trigger one of these events, uncheck Enable Host Monitoring to prevent vSphere
HA from triggering isolation response or network partition behaviors. Note the Enable Host
Monitoring check box shown in Figure 7.17; this is how you can temporarily disable the host-
monitoring function of vSphere HA during network maintenance so as not to trigger network
partition or network isolation behaviors.
Figure 7.17
Deselecting Enable
Host Monitoring
when performing
network mainte-
nance will prevent
vSphere HA from
unnecessarily trig-
gering network
isolation or network
partition responses.
Confi guring vSphere High Availability
After vSphere HA is enabled, coni guring vSphere HA revolves around several key areas:
Admission control and admission control policy
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VM options
VM monitoring
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Datastore heartbeating
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Each of these coni guration areas is described in detail in the following sections.
Configuring vSphere HA Admission Control
The vSphere HA Admission Control and Admission Control Policy settings control the behavior
of the vSphere HA-enabled cluster with regard to cluster capacity. Specii cally, should vSphere
HA allow the user to power on more VMs than it has capacity to support in the event of a
failure? Or should the cluster prevent more VMs from being powered on than it can actually
protect? That is the basis for the Admission Control—and by extension, the Admission Control
Policy—settings.
Admission Control has two settings:
Enable: Disallow VM power-on operations that violate availability constraints.
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Disable: Allow VM power-on operations that violate availability constraints.
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These options go hand in hand with the Admission Control Policy settings, which we'll
explain in a moment. First, though, let's take a closer look at the Admission Control settings.
Consider for a moment that you have a cluster of four identical ESXi hosts. Running on these
four ESXi hosts are a bunch of identically coni gured VMs. These VMs consume a total of 75
