6.0.1

CPUs that are used in host machines for fault tolerant VMs must be compatible with vSphere vMotion or
improved with Enhanced vMotion Compatibility. Also, CPUs that support Hardware MMU virtualization
(Intel EPT or AMD RVI) are required. The following CPUs are supported.
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Intel Sandy Bridge or later. Avoton is not supported.
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AMD Bulldozer or later.
Use a 10-Gbit logging network for FT and verify that the network is low latency. A dedicated FT network is
highly recommended.
Limits
In a cluster configured to use Fault Tolerance, two limits are enforced independently.
das.maxftvmsperhost
The maximum number of fault tolerant VMs allowed on a host in the cluster.
Both Primary VMs and Secondary VMs count toward this limit. The default
value is 4.
das.maxftvcpusperhost
The maximum number of vCPUs aggregated across all fault tolerant VMs on
a host. vCPUs from both Primary VMs and Secondary VMs count toward
this limit. The default value is 8.
Licensing
The number of vCPUs supported by a single fault tolerant VM is limited by the level of licensing that you
have purchased for vSphere. Fault Tolerance is supported as follows:
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vSphere Standard and Enterprise. Allows up to 2 vCPUs
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vSphere Enterprise Plus. Allows up to 4 vCPUs
NOTE FT and legacy FT are not supported in vSphere Essentials and vSphere Essentials Plus.
Fault Tolerance Interoperability
vSphere Fault Tolerance faces some limitations concerning the vSphere features, devices, and other features
it can interoperate with.
Before configuring vSphere Fault Tolerance, you should be aware of the features and products Fault
Tolerance cannot interoperate with.
vSphere Features Not Supported with Fault Tolerance
When configuring your cluster, you should be aware that not all vSphere features can interoperate with
Fault Tolerance.
The following vSphere features are not supported for fault tolerant virtual machines.
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Snapshots. Snapshots must be removed or committed before Fault Tolerance can be enabled on a
virtual machine. In addition, it is not possible to take snapshots of virtual machines on which Fault
Tolerance is enabled.
NOTE Disk-only snapshots created for vStorage APIs - Data Protection (VADP) backups are supported
with Fault Tolerance. However, legacy FT does not support VADP.
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Storage vMotion. You cannot invoke Storage vMotion for virtual machines with Fault Tolerance turned
on. To migrate the storage, you should temporarily turn off Fault Tolerance, and perform the storage
vMotion action. When this is complete, you can turn Fault Tolerance back on.
Chapter 3 Providing Fault Tolerance for Virtual Machines
VMware, Inc. 47