vSphere FT slow down the primary VM

Hello

I am trying the new FT that come with vSphere 6.0 cause I really need the feature for a CPU intensive server that I can't cluster, but all my tries are useless as the new FT is actually slow it down no matter how many vCPU.

Tried so far from 1vCPU to 4 vCPU, same or different datastore for the secondary VM and have 2 dedicated 1GB cards in a DVS with LACP and the log doesn't exceed the 100Mbs.

Thanks