vSphere FT slows down primary copy

[GiacomoNasi_IMA]

Hello everyone, I want to make fault tolerant a vm with windows server. When I turn the FT on from the vCSA, the performances start get so bad that I cannot use the vm GUI anymore.

I have 2 ESXi 6.7 hosts in the cluster, they are both nested on the same ESXi host. So the system is made of only one physical host and 2 virtual hosts.

While the ft is active, the RAM and the CPU usage of the 2 hosts are not overcommitted (I can see it from the graphs directly from the web clients of the hosts), so I cannot understand where is the problem. Also the communication latency shouldn't be a problem since we are on the same physical host.

Please give me some advices, until I'm stuck in this problem I cannot proceed in my university degree.

Thank you for you replies.

[daphnissov]

My advice is to use two physical hosts if you really want to use FT (especially if your degree is on the line). Nested virtualization is always going to be slower than bare metal, and that's especially true when you're doing something as intensive as FT. Get a second host and run ESXi on both directly.

[GiacomoNasi_IMA]

I can't have a second host, the place where I work has only one host for me

[a_p_]

How does the physical hardware look like, and how the virtual ESXi hosts regarding resources (CPU, RAM, ...), and the configuration (networking, storage, ...).

Remember that FT initially replicates the whole VM, which consumes resources. I the network, or the underlying storage becomes exhausted, thing may get really slow, which could explain what you experience.

Maybe you just need to remain patient until the initial synchronization is done!?

André