6.5.1

Table Of Contents
Solution
View the Advanced Runtime Info pane that appears in the vSphere HA section of the cluster's Monitor
tab in the vSphere Web Client. This information pane shows the slot size and how many available slots
there are in the cluster. If the slot size appears too high, click on the Resource Allocation tab of the
cluster and sort the virtual machines by reservation to determine which have the largest CPU and
memory reservations. If there are outlier virtual machines with much higher reservations than the others,
consider using a different vSphere HA admission control policy (such as the Percentage of Cluster
Resources Reserved admission control policy) or use the vSphere HA advanced options to place an
absolute cap on the slot size. Both of these options, however, increase the risk of resource fragmentation.
Fewer Available Slots Shown Than Expected
The Advanced Runtime Info box might display a smaller number of available slots in the cluster than you
expect.
Problem
When you select the Host Failures Cluster Tolerates admission control policy, view the Advanced
Runtime Info pane that appears in the vSphere HA section of the cluster's Monitor tab in the
vSphere Web Client. This pane displays information about the cluster, including the number of slots
available to power on additional virtual machines in the cluster. This number might be smaller than
expected under certain conditions.
Cause
Slot size is calculated using the largest reservations plus the memory overhead of any powered on virtual
machines in the cluster. However, vSphere HA admission control considers only the resources on a host
that are available for virtual machines. This amount is less than the total amount of physical resources on
the host, because there is some overhead.
Solution
Reduce the virtual machine reservations if possible, use vSphere HA advanced options to reduce the slot
size, or use a different admission control policy.
Troubleshooting Heartbeat Datastores
When the master host in a vSphere HA cluster can no longer communicate with a subordinate host over
the management network, the master host uses datastore heartbeating to determine if the subordinate
host might have failed or is in a network partition. If the subordinate host has stopped datastore
heartbeating, that host is considered to have failed and its virtual machines are restarted elsewhere.
vSphere Troubleshooting
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