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*VMware FT is available in the following versions of vSphere: Advanced, Enterprise, Enterprise Plus
*VMware FT requires virtual machines to have thick-eager zeroed disks. Thin or sparsely allocated disks will be converted to thick-eager zeroed when VMware FT is enabled requiring additional storage space. The virtual machine must be in a powered-off state to take this action.
*Ensure that the processors are supported: AMD Barcelona+, Intel Penryn+ (Download VMware SiteSurvey.)
Intel Xeon based on 45nm Core 2 Microarchitecture Category:
• 3100 Series
• 3300 Series
• 5200 Series (DP)
• 5400 Series
• 7400 Series
Intel Xeon based on Core i7 Microarchitecture Category:
• 5500 Series
AMD 3rd Generation Opteron Category:
• 1300 Series
• 2300 Series (DP)
• 8300 Series (MP)
*Virtual machines must be running on one of the supported guest operating systems. See the VMware knowledge base article 1008027 for more information.
*The combination of the virtual machine's guest operating system and processor must be supported by Fault Tolerance (for example, 32-bit Solaris on AMD-based processors is not currently supported).
*Ensure that HV (Hardware Virtualization) is enabled in the BIOS.
*Ensure that FT protected virtual machines are on shared storage (FC, iSCSI or NFS).
*Ensure that the datastore is not using physical RDM (Raw Disk Mapping). Virtual RDM is supported.
*Ensure that there is no requirement to use Storage VMotion for VMware FT VMs, since Storage VMotion is not supported for VMware FT VMs.
*Ensure that NPIV (N-Port ID Virtualization) is not used, since NPIV is not supported with VMware FT.
*Ensure that at least gigabit NICs are used. (10 Gbit NICs can be used as well as jumbo frames enabled for better performance.) Each host must have a VMotion and a Fault Tolerance Logging NIC configured. The VMotion and FT logging NICs must be on different subnets.
*Ensure that the primary and secondary ESX hosts and virtual machines are in an HA-enabled cluster.
*Ensure that there is no requirement to use DRS for VMware FT protected virtual machines; in this release VMware FT cannot be used with VMware DRS (although manual VMotion is allowed).
*Ensure that host certificate checking is enabled (enabled by default) before you add the ESX/ESXi host to vCenter Server.
*Ensure that the primary and secondary ESX/ESXi hosts are running the same build of VMware ESX/ESXi.
*Ensure that the virtual machines are NOT using more than 1 vCPU. (SMP is not supported.)
*Ensure that there is no user requirement to use NPT/EPT (Nested Page Tables/Extended Page Tables) since VMware FT disables NPT/EPT on the ESX host.
*Ensure that there is no user requirement to hot add or remove devices since hot plugging devices cannot be done with VMware FT.
*Ensure that there is no user requirement to use USB (USB must be disabled) and sound devices (must not be configured) since these are not supported for Record/Replay (and VMware FT.)
*Ensure that there is no user requirement to have virtual machine snapshots since these are not supported for VMware FT. Delete snapshots from existing virtual machines before protecting with VMware FT.
*Ensure that virtual machine hardware is upgraded to v7.
*Ensure that there are will be no more than four (to eight) VMware FT enabled virtual machine primaries or secondaries on any single ESX/ESXi host (suggested general guideline based on ESX/ESXi host and VM size and workloads which can vary.)
*Ensure that the virtual machines do not use a paravirtualized guest OS.
*Fault Tolerance is not supported with Paravirtual SCSI adapters.
*Ensure MSCS clustered virtual machines will have MSCS clustering removed prior to protecting with VMware FT.
*VMs can’t have any non-replayable devices (USB, sounds, physical CD-ROM, physical floppy)
*The virtual machine must not be a template.
*The virtual machine must not have VMware HA disabled.
*VMware Fault Tolerance requires a dedicated Gigabit Ethernet network between the physical servers, 10 Gigabit Ethernet should be considered if VMware FT is enabled for many virtual machines on the same host.
*There are no limits on how many virtual machines in a VMware DRS or VMware HA cluster can be enabled for VMware FT, but every machine with VMware FT enabled takes up twice as much capacity; this should be built into the configuration.
*Overhead is dependent on the workload and can be as low as 5% or as much as 20%.
*VMDirectPath is not available for FT virtual machines.
*When Fault Tolerance is turned on, vCenter Server unsets the virtual machine's memory limit and sets the memory reservation to the memory size of the virtual machine. While Fault Tolerance remains turned on, you cannot change the memory reservation, size, limit, or shares.
*Disabling the virtual machine restart priority setting for a fault tolerant virtual machine causes the Turn Off Fault Tolerance operation to fail. In addition, fault tolerant virtual machines with the virtual machine restart priority setting disabled cannot be deleted.
*VMCI stream socket connections are dropped when a virtual machine is put into Fault Tolerance (FT) mode. No new VMCI stream socket connections can be established while in FT mode.
*If firewalls or other controls exist between ESX hosts, ports 8100, 8200 (Outgoing TCP, incoming and outgoing UDP) must be open.
*A host must be certified by the OEM as FT-capable. Refer to the current Hardware Compatibility List (HCL) for a list of FT-supported servers.
*Some legacy network drivers are not supported. vmxnet2 is, but you might need to install VMware tools to access the vmxnet2 driver instead of vlance in certain guest operating systems.
*The hot plug device feature is automatically disabled for fault tolerant virtual machines. To hot plug devices, you must momentarily turn off Fault Tolerance, perform the hot plug, and then turn on Fault Tolerance.
*Extended Page Tables (EPT)/Rapid Virtualization Indexing (RVI) is automatically disabled for virtual machines with Fault Tolerance turned on.
*When you upgrade hosts that contain fault tolerant virtual machines, ensure that the Primary and Secondary VMs continue to run on hosts with the same ESX/ESXi version and patch level.
*Ensure that a resource pool containing fault tolerant virtual machines has excess memory above the memory size of the virtual machines. Fault tolerant virtual machines use their full memory reservation. Without this excess in the resource pool, there might not be any memory available to use as overhead memory.
*VMware recommends that you use a maximum of 16 virtual disks per fault tolerant virtual machine.
*To ensure redundancy and maximum Fault Tolerance protection, VMware recommends that you 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.
*Too Much Activity on VMFS Volume Can Lead to Virtual Machine Failovers - reduce the number of file system operations or ensure that the fault tolerant virtual
machine is on a VMFS volume that does not have an abundance of other virtual machines that are regularly being powered on, powered off, or migrated using VMotion.
*Software virtualization with FT is unsupported.
*FT requires that the hosts for the Primary and Secondary VMs use the same CPU model, family, and stepping.
*Hosts running the Primary and Secondary VMs should operate at approximately the same processor frequencies, otherwise the Secondary VM might be restarted more frequently. Platform power management features which do not adjust based on workload (for example, power capping and enforced low frequency modes to save power) can cause processor frequencies to vary greatly.
*Apply the same instruction set extension configuration (enabled or disabled) to all hosts.
*Snapshots are not supported. Client agents may be required for backup.
*VMware Consolidated Backup (VCB) is not supported with Fault Tolerance - A VCB backup performed on an FT-enabled virtual machine powers off both the primary and the secondary virtual machines and might render the virtual machines unusable.
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