1.VMware FT is available after versions of vSphere Advanced version (Advanced, Enterprise, Enterprise Plus)
2.Hardware Virtualization should be enabled in the BIOS
3.CPU should be compatible with FT. Please refer VMware site for supported processors.
4.FT enabled virtual machines should be placed in Shared storage (FC,ISCSI or NFS)
5. FT virtual machines should be placed in HA enabled cluster
6. FT cannot be used with DRS in vsphere 4.0 but FT is fully now integrated with DRS from vSphere 4.1
7. In vsphere 4.0, primary and secondary ESX should have same ESX version and patch level. This limitation is no more from vSphere 4.1. The primary and secondary ESX need not be at same build and
patch level because FT has its own version associated with it.
8. Only 4 FT protetcted virtual machines is allowed per ESX/ESXi host.
9. vMotion and FT Logging should be enabled in vmkernel portgroup of the virtual machine (Separate NIC for vMotion & FT logging is recommeneded along with NIC teaming)
10. Host certificate checking should be enabled (enabled by default)
11. Dedicated 10 GB ethrenet card between ESX servers will give best performance results.
12. FT ports 8100, 8200 (Outgoing TCP, incoming and outgoing UDP) must be open if any firewall exist between ESX hosts
13. Minimum of 3 hosts in HA enabled cluster is the requirement for running FT protected virtual machines but 2 hosts is the strong requirement.
14. FT virtual Machines cannot be backed up using the backup technology like (VCB, vmware data recovery),which uses snapshot feature.
15. NPIV (N-PortID Virtualization) is not supported with vmware FT
16. USe Redundancy at all layers(like NIC teaming, multiple network switches, and storage multipathing) to fully utilize the FT features.
17. MSCS clustering is not supported with VMware Fault Tolerance.
18. In vSphere 4.0, Manual vmotion is allowed but automatic load balance using vmotion by DRS is fully supported from vSphere 4.1
19. We cannot use storage vmotion (SVmotion) to migrate FT protected virtual machines from one datastore to another.
20. EVC (enhanced vmotion compatibility) should be enabled in DRS cluster to utilize the automatic load balancing feature provided by DRS for the FT protected virtual machine.
Please refer my blog post on Virtual Machine Requirements for VMware Fault Tolerance
Thanks For Reading!!!