6.0.1

Host Requirements for Fault Tolerance
You must meet the following host requirements before you use Fault Tolerance.
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Hosts must use supported processors.
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Hosts must be licensed for Fault Tolerance.
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Hosts must be certified for Fault Tolerance. See
http://www.vmware.com/resources/compatibility/search.php and select Search by Fault Tolerant
Compatible Sets to determine if your hosts are certified.
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The configuration for each host must have Hardware Virtualization (HV) enabled in the BIOS.
NOTE VMware recommends that the hosts you use to support FT VMs have their BIOS power management
settings turned to "Maximum performance" or "OS-managed performance".
To confirm the compatibility of the hosts in the cluster to support Fault Tolerance, you can also run profile
compliance checks as described in “Create Cluster and Check Compliance,” on page 51.
Virtual Machine Requirements for Fault Tolerance
You must meet the following virtual machine requirements before you use Fault Tolerance.
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No unsupported devices attached to the virtual machine. See “Fault Tolerance Interoperability,” on
page 47.
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Incompatible features must not be running with the fault tolerant virtual machines. See “Fault
Tolerance Interoperability,” on page 47.
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Virtual machine files must be stored on shared storage. Acceptable shared storage solutions include
Fibre Channel, (hardware and software) iSCSI, NFS, and NAS.
Other Configuration Recommendations
You should also observe the following guidelines when configuring Fault Tolerance.
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If you are using NFS to access shared storage, use dedicated NAS hardware with at least a 1Gbit NIC to
obtain the network performance required for Fault Tolerance to work properly.
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The memory reservation of a fault tolerant virtual machine is set to the VM's memory size when Fault
Tolerance is turned on. Ensure that a resource pool containing fault tolerant VMs has memory resources
above the memory size of the virtual machines. Without this excess in the resource pool, there might
not be any memory available to use as overhead memory.
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Use a maximum of 16 virtual disks per fault tolerant virtual machine.
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To ensure redundancy and maximum Fault Tolerance protection, you should have a minimum of three
hosts in the cluster. In a failover situation, this provides a host that can accommodate the new
Secondary VM that is created.
Configure Networking for Host Machines
On each host that you want to add to a vSphere HA cluster, you must configure two different networking
switches (vMotion and FT logging) so that the host can support vSphere Fault Tolerance.
To enable Fault Tolerance for a host, you must complete this procedure for each port group option (vMotion
and FT logging) to ensure that sufficient bandwidth is available for Fault Tolerance logging. Select one
option, finish this procedure, and repeat the procedure a second time, selecting the other port group option.
vSphere Availability
50 VMware, Inc.