If your FT network is not optimally configured, you might experience latency problems with the FT VMs.
FT VMs might see a variable increase in packet latency (on the order of milliseconds). Applications that demand very low network packet latency or jitter (for example, certain real-time applications) might see a degradation in performance.
Some increase in network latency is expected overhead for Fault Tolerance, but certain factors can add to this latency. For example, if the FT network is on a particularly high latency link, this latency is passed on to the applications. Also, if the FT network has insufficient bandwidth (fewer than 10 Gbps), greater latency might occur.
Verify that the FT network has sufficient bandwidth (10 Gbps or more) and uses a low latency link between the Primary VM and Secondary VM. These precautions do not eliminate network latency, but minimize its potential impact.