I have an ESX host with 32 GB of RAM.
Placing three VMs on it, allocating each one to 16 GB RAM each - knowingly overcommitting the total.
Each VM has two network interfaces.
The first connects to a virtual switch called frontend and has an uplink NIC to a physical network.
The second connects to a virtual "switch-in-a-box" - i.e. no physical uplinks for this switch, and we call this network backend.
When the three machines are under load, the ESX vmkernel begins to swap some RAM out to disk - up to 6.5GB.
I cannot find any documentation/reasoning in regards to the backend network's performance degrading due to the heavier load due to memory swapping, but that is basically the impact.
Is there any clear reference regarding virtual switch speeds without any uplinks?