Hey there! If you‘re an owner of a Minecraft server, you may have experienced the frustration of your server suddenly freezing up on you and your players. Server freezes can cause disruptive downtime, lost progress, and unhappy players, so you probably want to get things running smoothly again ASAP.
Not to worry – I‘ve been hosting Minecraft servers for over 5 years, and in this guide, I‘ll walk you through exactly how to troubleshoot and prevent server freezes. We‘ll cover:
- Common causes of Minecraft server freezes
- Steps to unfreeze and recover a frozen server
- Expert tips to optimize your server and avoid future freezes
- Detailed troubleshooting for specific freeze scenarios
Let‘s get your server back up and running!
Why Does My Minecraft Server Freeze?
Before we can fix your freezing issues, it helps to understand what causes Minecraft servers to lock up in the first place. From my experience, here are the most common culprits:
1. Insufficient Server Hardware
Minecraft servers require pretty beefy hardware to run smoothly, especially for servers with lots of players and mods. Here are some benchmarks from hosting experts:
- RAM: 4GB minimum recommended for 5-20 players. 8-16GB+ for modpacks.
- CPU: At least a modern quad core like an Intel i5. More cores help – aim for 6-8 cores on bigger servers.
- Disk: NVMe SSDs provide much faster read/write speeds for chunk saving.
If your hardware can‘t keep up with all the chunks loading and game logic, freezing is almost inevitable. Upgrading to faster gear can help resolve hardware lag.
2. Software Bugs/Conflicts
Issues in Minecraft, server platforms like Spigot or Bukkit, mods, and plugins can trigger freezes when they hit certain conditions. Keeping all your software up-to-date avoids most known freezing bugs.
Conflicts from VPNs, firewalls, anti-cheat mods, backup software and the like interfering with the server connection are also common, so check for clashes.
3. Garbage Collection Pauses
Minecraft servers do "garbage collection" periodically to free up RAM, which can freeze servers if they don‘t have enough memory to do this smoothly.
Allocate at least 8GB RAM and use flags like -XX:+UseG1GC to make garbage collection quicker and prevent these stalls.
4. World Generation Slowdowns
Exploring new areas trigers world generation, which can lag the server as new chunks populate. This is especially true in modpacks with complex terrain and structure generation.
Pre-generating the world spawn area and heavily used dimensions smooths out this on-demand chunk creation and avoids associated freezing.
5. Damaged/Corrupted World Data
Certain mods and duplication glitches can slowly corrupt world data over time. Trying to load damaged chunks then leads to hangs and lockups. Reverting to a good backup or wiping glitched chunks alleviates this.
By understanding the most common sources of Minecraft server freezes, hopefully you can start to narrow down what‘s causing your freezing issues specifically. Now let‘s look at how to recover when your server seizes up.
How to Unfreeze and Recover a Frozen Minecraft Server
When your Minecraft server stops responding and players start getting disconnected, here are some troubleshooting steps I‘d recommend to try and revive it:
1. Run a Server Restart
A full restart will clear any memory issues and reset stuck threads. Stop the server safely with stop rather than just killing the process if possible, to allow data to save.
- Chance of success: High, but disruptive with downtime.
2. Reload Configs
Connect to console and run /reload – this reloads configs and restarts the main thread, potentially unfreezing the server without a full restart.
- Chance of success: Medium. Kicks players but no saves/data loss.
3. Identify and Stop Stuck Threads
Check logs for a thread dump, then run kill -SIGINT <thread ID> on any threads eating CPU. This can terminate runaway tasks without a full stop.
- Chance of success: Medium if a thread is clearly stuck.
4. Add More RAM
If freezes happen during garbage collection, stop the server and increase the RAM allocation to give the JVM breathing room.
- Chance of success: Medium if hardware allows more memory.
5. Roll Back Software Changes
If issues started after updating or adding mods/plugins, revert those changes and try loading the server without them to narrow down conflicts.
- Chance of success: High if a problematic update triggered freezes.
6. Restore World From Backup
For really stubborn freezing, revert to a known good backup to resolve deeper world corruption that is hard to fix on a live server.
- Chance of success: High for world data-related freezes.
Using the right steps for your situation, you can get your server back online faster. But it also helps to follow some best practices to avoid freezes in the first place.
Optimizing Your Server to Prevent Freezes
While not every freeze is avoidable, there are some configuration tweaks and mods from the Minecraft hosting community that can reduce how often your server seizes up:
Use Server Performance Monitoring Tools
Plugins like Spark and Watchdog allow you to monitor TPS, memory usage, tick times and other metrics to catch performance issues early.
Set warnings when TPS drops too low or RAM usage spikes too high and you can stay ahead of problems before they snowball into a full freeze.
Tune Your Server‘s server.properties File
There are a few key settings here that really impact performance:
view-distance – Lower than the default 10 chunks. 4-6 is a good balance for most servers.
simulation-distance – Match this to view-distance, no need to simulate more than players can see.
sync-chunk-writes – Set to
false– speeds up writes but risks some data loss on crashes.max-tick-time – Lower from the default 50ms, try 30ms to keep things smooth.
Install Server Mods to Optimize and Protect World Data
Helpful optimization mods include:
Lithium – Various optimizations to improve server tick speeds.
Phosphor – Better lighting engine performance, especially for modpacks.
Spark – Detailed server metrics to help configure for peak performance.
Chunky – Pre-generates chunks around the spawn to reduce player join lag.
Protection mods like CoreProtect can also roll back and restore world data if it gets corrupted by glitches or crashes.
Upgrade Your Server Hardware (If Possible)
While you can tweak settings to optimize performance, there‘s no replacement for sufficient hardware capacity:
RAM: Shoot for at least 8GB, or up to 16GB for heavily moded servers.
CPU: Faster single core speed helps with the main server thread. 4 cores minimum, 6-8 ideal for 20+ players.
Storage: SSDs provide much quicker world data access. PCIe NVMe drives are fastest.
Check your server metrics – if RAM or CPU is constantly pinned high, upgraded hardware can really help avoid freezes before they occur.
Troubleshooting Tricky Causes of Freezing
Sometimes general optimizations aren‘t enough – you need to dig in and troubleshoot some tricky situations that can bring Minecraft servers to their knees:
Players Can‘t Join – Freezing on Connect
Check server logs – authentication issues can prevent logins. Set
online-modetofalsetemporarily to narrow down problems.Ensure your router, firewalls and cloud provider are not blocking connections to the server. Open ports, add exceptions for the server.
Lower
view-distanceinserver.propertiesso less chunks load on join.Verify your network has enough bandwidth to handle chunk transfers on join.
Mob Farms Overwhelming the Server
Add clearlag plugins to limit total mobs and automatically cull excessive entities.
Tweak mob farm timers and storage to throttle maximum mob counts. Don‘t let crammed pens freeze servers.
Set a lower
mob-spawn-rangeinserver.propertiesto constrain natural spawns.Encourage players to limit size of farms/pens. Some mods allow entity count permissions per player.
Redstone Machines and Contraptions Freezing
Avoid large complex redstone circuits with lots of entities and lighting updates. These tax servers immensely.
Limit scale of individual redstone contraptions – smaller groups of machines spread out is better.
Set up sandbox test dimensions for large redstone builds to keep them isolated from live server.
Add supporting mods like Carpet, Phosphor, Lithium, and Krypton to optimize redstone logic.
Large Player Bases Causing Regional Freezing
Encourage players to spread out and not cluster too many large bases in one area.
Reset overloaded regions around major bases to refresh terrain, entities, lighting, etc. Backup first!
Limit village sizes and active portals to reduce entity/lighting load.
Pregenerate the area around large bases to reduce lag as players explore nearby.
Hopefully these tips will help you isolate and resolve some of those trickier freezing scenarios based on your server‘s specific issues.
The key is continuously monitoring performance, establishing limits that maintain a stable server, and not being afraid to reset problematic areas or builds when things get out of hand. Let‘s wrap up with a quick summary of what we covered today.
Let‘s Review What We Learned
Common freezing culprits are insufficient hardware, software conflicts, memory issues, chunk generation, and data corruption.
Take proactive steps like pregenerating terrain, limiting entities, and optimizing configs to avoid freezes.
When freezing hits, a restart/reload, more RAM, or reverting changes may be able to revive a frozen server.
For stubborn issues, restore world backups, wipe glitched data, or reinstall server software as needed.
Monitor server health metrics, update software, and troubleshoot specific scenarios like mob farms to stop recurring freezes.
Upgrade RAM, CPU cores, and storage if hardware limitations underly freezing issues.
Hopefully with these troubleshooting tips and preventative measures, you‘ll be able to keep your Minecraft server running smooth and minimize disruption when performance issues do pop up. Let me know if any problems persist – I‘m happy to help fellow server admins squash those pesky freezing bugs!
