vSphere 6.5 Fault Tolerance also introduced with a lot of new improvements especially with improved latency handling with the release of vSphere 6.5.

Benefits of VMware Fault Tolerance

  • Continuous Availablity with Zero downtime and Zero data loss
  • NO TCP connections loss during failover
  • Fault Tolerance is completely transparent to Guest OS.
  • FT doesn’t depend on Guest OS and application
  • Instantaneous Failover from Primary VM to Secondary VM in case of ESXi host failure

DRS Integration improved with Fault Tolerance:


vSphere 6.5 Fault Tolerance (FT) has more integration with DRS, which helps the better placement decisions by ranking the ESXi hosts based on the available network bandwidth as also it recommends the datastore to place the Secondary VM VMDK files.

As We already talked about Network Aware DRS in vSphere 6.5 HA & DRS article. With Network Aware DRS, DRS will now consider the network bandwidth on the ESXi hosts before placing new Virtual machines on the ESXi host and also during VM migrations to the ESXi host. DRS will check Tx and Rx rates of the connected physical uplinks and avoids placing VMs on hosts that are greater than 80% utilized. It uses the network utilization information as the additional check to determine the destination ESXi is suitable for VM placement and migration. This option improves the DRS placement decisions.

Lower Network Latency:


There are more efforts put on vSphere 6.5 Fault Tolerance to lower the network latency. This will improve the performance to impact to certain types of applications that were sensitive to the additional latency first introduced with vSphere 6.0 FT. This improvement gives more opportunity to Protect mission-critical applications using Fault Tolerance.

Multi-NIC Fault Tolerance Support:


You can now configured FT networks to use multiple Network adapters (NICs) to increase the overall bandwidth for FT logging traffic. This works similar to the Multi-NIC vMotion provides more bandwidth for FT network.

And the difference between 5.5 and 6.0: