6.0.1

Table Of Contents
Solution
If the ESXi server hardware supports HV, but HV is not currently enabled, enable HV in the BIOS on that
server. The process for enabling HV varies among BIOSes. See the documentation for your hosts' BIOSes for
details on how to enable HV.
If the ESXi server hardware does not support HV, switch to hardware that uses processors that support
Fault Tolerance.
Compatible Hosts Not Available for Secondary VM
If you power on a virtual machine with Fault Tolerance enabled and no compatible hosts are available for its
Secondary VM, you might receive an error message.
Problem
You might encounter the following error message:
Secondary VM could not be powered on as there are no compatible hosts that can accommodate it.
Cause
This can occur for a variety of reasons including that there are no other hosts in the cluster, there are no
other hosts with HV enabled, Hardware MMU Virtualization is not supported by host CPUs, data stores are
inaccessible, there is no available capacity, or hosts are in maintenance mode.
Solution
If there are insufficient hosts, add more hosts to the cluster. If there are hosts in the cluster, ensure they
support HV and that HV is enabled. The process for enabling HV varies among BIOSes. See the
documentation for your hosts' BIOSes for details on how to enable HV. Check that hosts have sufficient
capacity and that they are not in maintenance mode.
Secondary VM on Overcommitted Host Degrades Performance of Primary VM
If a Primary VM appears to be executing slowly, even though its host is lightly loaded and retains idle CPU
time, check the host where the Secondary VM is running to see if it is heavily loaded.
Problem
When a Secondary VM resides on a host that is heavily loaded, the Secondary VM can affect the
performance of the Primary VM.
Cause
A Secondary VM running on a host that is overcommitted (for example, with its CPU resources) might not
get the same amount of resources as the Primary VM. When this occurs, the Primary VM must slow down to
allow the Secondary VM to keep up, effectively reducing its execution speed to the slower speed of the
Secondary VM.
Solution
If the Secondary VM is on an overcommitted host, you can move the VM to another location without
resource contention problems. Or more specifically, do the following:
n
For FT networking contention, use vMotion technology to move the Secondary VM to a host with fewer
FT VMs contending on the FT network. Verify that the quality of the storage access to the VM is not
asymmetric.
n
For storage contention problems, turn FT off and on again. When you recreate the Secondary VM,
change its datastore to a location with less resource contention and better performance potential.
vSphere Troubleshooting
14 VMware, Inc.