Unfortunately that would not be possible, server does not have a gui, it is running headless factorio only

Yes, you would have to install the normal version on it.

Alternatively check if the low fps issue persist if you run the game at half speed with the command: /c game.speed = 0.5

I ...

What other factors would you consider? I am working in IT for 15 years, and that would be my first case where server CPU is bottleneck and underutilized at the same time

Actually I was able to narrow down the issue to 250k idle logistic bots on Fulgora. 20k of them were waiting for free roboport slots. After placing them in storage chests, FPS/UPS is 60/60 again.

But I still have doubts, how server can be the bottleneck, if load was never higher than 3 per 8 cores

so you are telling me, that server is a bottleneck? So why factorio is not utilizing whole cpu?
https://i.ibb.co/xq836F8K/htop.png

> Try running the save in single player on the server machine if that is possible and post a screenshot of that.
Unfortunately that would not be possible, server does ...

fan1: 3400 RPM
fan2: 3400 RPM
CPU: +72.0°C
GPU: +59.0°C
temp3: +53.0°C
temp4: +0.0°C
temp5: +0.0°C
temp6: +0.0°C
temp7: +0.0°C
temp8: N/A

do you believe that server cpu might be a limiting factor of client fps? it is little surprising to me
server ups is even higher than client ups

server load is ...

sure, here are:
- single player screenshoot https://i.ibb.co/Y4Jbq5Tf/single-player.png
- single player log: https://www.dropbox.com/scl/fi/psk87utx3snjeh8uhk2k3/factorio-current-single-player.log?rlkey=vcla2b6olrxek0frj638a5umd&st=620q99nw&dl=0
- multiplayer - server - log: https://www.dropbox.com ...

Just checked, in single player I have both UPS and FPS at 46

i am adding more information:
- another screenshoot: https://i.ibb.co/yBP1FXWr/factorio.png
- log file: https://www.dropbox.com/scl/fi/8v3n2ahv9aor9xxflm0hr/factorio-current.log?rlkey=kpz69282kpt12ozr5sy38el99&st=6b7w4sxl&dl=0
- save: https://www.dropbox.com/scl/fi/8wdlunykhw6nzjm1gag2p/perf.zip ...

Hi
Can you please help debug my issue? It might be connected to about 20k of logistic robots, not sure

Can you tell me if attached info is enough to determine what is causing the lag?