6.5.1

Table Of Contents
Another possible cause of this problem is if your cluster contains any virtual machines that have much
larger memory or CPU reservations than the others. The Host Failures Cluster Tolerates admission
control policy is based on the calculation on a slot size consisting of two components, the CPU and
memory reservations of a virtual machine. If the calculation of this slot size is skewed by outlier virtual
machines, the admission control policy can become too restrictive and result in a red cluster. In this case,
you can use the vSphere HA advanced options to reduce the slot size, use a different admission control
policy, or modify the policy to tolerate fewer host failures.
Solution
Check that all hosts in the cluster are healthy, that is, connected, not in maintenance mode and free of
vSphere HA errors. vSphere HA admission control only considers resources from healthy hosts.
Unable to Power On Virtual Machine Due to Insucient Failover
Resources
You might get a not enough failover resources fault when trying to power on a virtual machine in a
vSphere HA cluster.
Problem
If you select the Host Failures Cluster Tolerates admission control policy and certain problems arise, you
might be prevented from powering on a virtual machine due to insufficient resources.
Cause
This problem can have several causes.
n
Hosts in the cluster are disconnected, in maintenance mode, not responding, or have a vSphere HA
error.
Disconnected and maintenance mode hosts are typically caused by user action. Unresponsive or
error-possessing hosts usually result from a more serious problem, for example, hosts or agents have
failed or a networking problem exists).
n
Cluster contains virtual machines that have much larger memory or CPU reservations than the
others.
The Host Failures Cluster Tolerates admission control policy is based on the calculation on a slot size
comprised of two components, the CPU and memory reservations of a virtual machine. If the
calculation of this slot size is skewed by outlier virtual machines, the admission control policy can
become too restrictive and result in the inability to power on virtual machines.
n
No free slots in the cluster.
Problems occur if there are no free slots in the cluster or if powering on a virtual machine causes the
slot size to increase because it has a larger reservation than existing virtual machines. In either case,
you should use the vSphere HA advanced options to reduce the slot size, use a different admission
control policy, or modify the policy to tolerate fewer host failures.
vSphere Troubleshooting
VMware, Inc. 44