VMware vSphere 4.x and 5.x offers Legacy Fault Tolerance (Legacy FT) that supports uniprocessor virtual machines. Legacy FT requires a separate fault tolerance certification by server partners in order to be officially supported.

 

VMware vSphere 6.0 offers a new technique for Fault Tolerance (FT) that supports both uniprocessor and multiprocessor virtual machines and is the default for vSphere 6.0 ESXi hosts. Though, Legacy FT is still supported in vSphere 6.0 for backward compatibility with pre-existing virtual machines, customers are encouraged to discontinue its use. vSphere 6.0 FT does not require a separate certification. However, server partners can optionally run separate certification for legacy FT in vSphere 6.0.

 

VMware is phasing out legacy FT and will not be offering it on new processor generations launched after Q1’2015 in any vSphere release. This means that legacy FT will not be extended to include support for Intel Xeon E3-1200-v4, E3-1200-v5, Xeon D-1500, and any future Intel processors for any vSphere 5.x or 6.x release.

 

Switching n uniprocessor virtual machine from legacy FT to the new form of FT is a simple operation and is expected to benefit virtual machine performance. For more information on this process, see the Using Fault Tolerance section of the vSphere Availability guide.