6.5.1

Table Of Contents
Table 32. Differences Between Legacy FT and vSphere FT (Continued)
Legacy FT vSphere FT
Eager-zeroed thick .vmdk disk les Required Not required because vSphere FT
supports all disk le types, including
thick and thin
.vmdk redundancy Only a single copy Primary VMs and Secondary VMs
always maintain independent copies,
which can be placed on dierent
datastores to increase redundancy.
NIC bandwidth Dedicated 1-Gb NIC recommended Dedicated 10-Gb NIC recommended
CPU and host compatibility Requires identical CPU model and
family and nearly identical versions
of vSphere on hosts.
CPUs must be compatible with
vSphere vMotion or EVC. Versions of
vSphere on hosts must be compatible
with vSphere vMotion.
Turn on FT on running VM Not always supported. You might
need to power o VM rst.
Supported
Storage vMotion Supported only on powered-o VMs.
vCenter Server automatically turns
o FT before performing a Storage
vMotion action and turns on FT again
after the Storage vMotion action
completes.
Not supported. User must turn o
vSphere FT for the VM before
performing the Storage vMotion action
and turn on vSphere FT again.
vlance networking drivers Not supported Supported
Additional Requirements for Legacy FT
In addition to the dierences listed for legacy FT, it also has the following unique requirements.
n
ESXi hosts must have access to the same virtual machine datastores and networks.
n
Virtual machines must be stored in virtual RDM or virtual machine disk (VMDK) les that are thick
provisioned. If a virtual machine is stored in a VMDK le that is thin provisioned and an aempt is
made to use fault tolerance, a message appears. It indicates that the VMDK le must be converted. To
perform the conversion, you must power o the virtual machine.
n
Hosts must have processors from the vSphere FT-compatible processor group. Verify that the hosts'
processors are compatible with one another.
n
The host that supports the Secondary VM must have a processor that supports fault tolerance and is the
same CPU family or model as the host that supports the Primary VM.
n
When upgrading hosts that contain fault tolerant VMs, verify that the Primary and Secondary VMs
continue to run on hosts with the same FT version number or host build number. This requirement
applies to hosts before ESX/ESXi 4.1.
N If you designated a VM to use legacy FT before you upgraded the hosts in the cluster, that VM
continues to use legacy FT after the host upgrade.
Upgrading Hosts Involved with Legacy FT
To upgrade your hosts to vSphere 6.5 or later, you must turn o legacy FT on all aected VMs or move those
VMs to other hosts. If you do not prepare for the upgrade in this way, VMware vSphere Update Manager
blocks the upgrade.
vSphere Availability
54 VMware, Inc.