Ban auto miners (ships that use scripts and autopilot to mine). Mining has historically been the main source of slowdown in sim speed, which is why the voxel updates are so slow (far apart) when mining now.
Set a limit on drills per ship if you have to. Every drill being used causes an update. The ships with 50 drills might look epic, they will negatively affect your sim speed. Get a drill mod that lets you do more with one drill.
Ask that scripts on timers be set to run as infrequently as possible. There's no need to have automatic configurable LCDs updating 50 panels every second on a large station or ship, when every 3-5 seconds will do.
Turrets are another major cause of lag. Consider a limit on the number allowed per ship/station, as 20 turrets on a large ship constantly hunting for targets will hurt your performance.
Clean up your server as well. Get SEToolbox, download the save and open it up. See how much useless junk there is, and get rid of what you can.
Consider some admin tools/scripts that can perform these functions for you, like disabling turrets, clearing assembler queues, stopping moving objects etc.
Also see section "How to clean your Space Engineers world file"
The way Space Engineers dedicated servers are programmed, the maximum CPU the game server can use is one core. Once this limit is hit, you will start to experience a drop in sim speed, lags and at worse server crashes.
While we provide top hardware with plenty of resources free for your game server, you will still reach a limit due to the Space Engineers dedicated server software.
Once this happens, you need to reduce the objects that float around in your world and run a cleanup. We will briefly describe a few ways to do that.
There are several programs that let you clean up your world: SE Toolbox, SpaceMaster and Server Extender.
Download the world folder located at /SE[Number]/SpaceEngineers/Saves/[your current world name]/
Open the world in SE Toolbox
Once open in SE Toolbox, you can see all objects that exist in your game world. Ships, floating objects, distances of all these items and more.
With a cleanup you are looking for ships that have drifted far away from the area you are working, floating objects, Auto generated ships. You can also run resource reports, showing whatthe world has in it by item. Lots of turrets / rotors or other resource intensive blocks can cause trouble in the world.
Deleting floating objects: Order the list by type, CTRL + CLICK the top floating object. Then find the bottom floating object of the list and press CTRL + SHIFT + CLICK. This should highlight them all. Then click delete (red cross) on the tool bar.
Checking for drifting ships/items: Order the list by distance, further the distance the more resources used on generating a bigger world, we advise to ensure everythign is kept to witihin 1000KM and expand as required. Infinite worlds need to monitor for drifting items/ships.
Ships: If you have auto generating mods for ships, we advise that you RENAME ships to ***KEEEP*** so when it comes to clean ups you can just select unwanted ships and delete.
Resource Report: Click WORLD > REPORT ALL RESOURCES. A new window will open, click GENERATE REPORT. This generates a report of the world showing item numbers, block types and lots more.
To get your cleaned up world back on the server, follow these steps:
Upload the files in your world folder to this folder in your FTP account: /SE[Number]/SpaceEngineers/Saves/[your current world name]/
Start your server
Space Master is an ingame admin tool used by pressing ALT+F10 it allows you to search through entities in the world and delete them, including deleting floating objects. There is alot of options for this tool but not much documentation so feel free to play around with it. If you use it and delete something you wanted we are unable to do anything about it so make sure you know what you are deleting. This official video from Keen gives you an overview.
If you use Server Extender provides several ways to maintain and clean the world for you.
Log in to your nc1.eu control panel, click on your desired Space Engineers server
Stop your server
Scroll down to the "SE Server Extender" box, and click "Edit..."
Set the "Activate SE Server Extender" option to "Yes"