Why Your Minecraft 1.21.1 Server is Running Slower Than It Should
Minecraft 1.21.1 introduced some fantastic features, but let’s be honest—it also brought performance challenges that can turn your smooth server into a laggy mess. If you’re seeing TPS drops below 20, players complaining about rubber-banding, or your server console lighting up with warnings, you’re not alone. The good news? Most performance issues have straightforward fixes.
Quick answer: Minecraft 1.21.1 server performance optimization focuses on three core areas: proper JVM flag configuration, chunk loading management, and entity reduction. By adjusting your server’s memory allocation, pre-generating your world, and limiting mob farms, you can typically improve TPS (ticks per second) by 30-50% without sacrificing gameplay quality.
JVM Arguments That Actually Matter
Your Java Virtual Machine flags are the foundation of server performance. Vanilla Minecraft’s default JVM arguments are designed for client-side play, not dedicated servers handling multiple players simultaneously.
Memory Allocation Settings
The most common mistake server owners make is throwing more RAM at the problem. Here’s what actually works:
- Xms and Xmx should match – Set both to the same value to prevent garbage collection stutters
- Don’t over-allocate – 8GB is plenty for most servers under 20 players
- Leave headroom – If your VPS has 16GB RAM, allocate 12GB maximum to Minecraft
Here’s a solid JVM argument string for a server with 8GB allocated:
java -Xms8G -Xmx8G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true -jar server.jar nogui
These are Aikar’s flags, battle-tested by thousands of servers. They optimize garbage collection specifically for Minecraft’s memory usage patterns.
Choosing the Right Java Version
Minecraft 1.21.1 requires Java 21 or newer. Don’t use older versions—they’re not just unsupported, they’re significantly slower. OpenJDK and Oracle Java both work fine, but GraalVM offers about 10-15% better performance if you want to get technical.
Server.properties Configuration for Performance
Your server.properties file controls fundamental gameplay mechanics that directly impact performance. Here are the settings that matter most:
View Distance and Simulation Distance
View distance determines how far players can see. Simulation distance controls how far away chunks actually process entities, redstone, and crop growth. Most servers set these too high.
| Setting | Default | Recommended | Impact |
|---|---|---|---|
| view-distance | 10 | 6-8 | Reduces network bandwidth and chunk loading |
| simulation-distance | 10 | 4-6 | Massive CPU savings on entity processing |
Dropping simulation distance from 10 to 6 can improve server TPS by 20-30% without players noticing much difference. Entities beyond simulation distance simply pause—they don’t despawn or disappear.
Entity and Spawn Limits
Entities are performance killers. Every zombie, item frame, and dropped item requires processing every tick.
- max-entity-cramming: Set to 8 (prevents mob farm lag)
- entity-broadcast-range-percentage: Set to 80-90 (reduces network overhead)
- spawn-limits: Reduce monster and animal spawns by 20-30% from defaults
Need reliable hosting that handles these optimizations out of the box? GameTeam.io offers optimized Minecraft servers starting at $1/GB—grab 20% off with our limited-time offer.
Paper, Purpur, or Vanilla? Server Software Comparison
Your server software choice is probably the single biggest performance decision you’ll make.
Vanilla is Mojang’s official server. It works, but it’s not optimized for anything beyond small friend groups. You’re missing out on 50-70% potential performance.
Paper is the gold standard. It’s a high-performance fork that maintains plugin compatibility while adding aggressive optimizations. Expect 2-3x better performance than vanilla with identical gameplay.
Purpur builds on Paper with additional configuration options and gameplay tweaks. It’s slightly more aggressive with optimizations and gives you granular control over almost everything.
Fabric with optimization mods (Lithium, Phosphor, Starlight) offers performance comparable to Paper but with different mod compatibility. Good for modded servers.
For most servers, Paper or Purpur is the obvious choice. They’re stable, well-maintained, and the performance gains are immediate and dramatic.
Chunk Management and World Pre-Generation
World generation is incredibly CPU-intensive. When players explore new areas, your server has to generate chunks on the fly, causing lag spikes and TPS drops.
Pre-Generate Your World
Use Chunky (a plugin) to pre-generate your world before players join:
- Install Chunky on your Paper/Purpur server
- Run
/chunky radius 5000(adjust size as needed) - Run
/chunky start - Let it complete—this might take hours
A 10,000 block radius (5,000 in each direction) is reasonable for most survival servers. This prevents exploration lag entirely.
Set a World Border
After pre-generation, set a world border to match: /worldborder set 10000
This prevents players from forcing new chunk generation and keeps your world file size manageable.
Plugin and Mod Optimization
Poorly coded plugins destroy server performance. Use Spark (a profiling plugin) to identify which plugins are eating your CPU.
Common Performance-Killing Plugins
- Holographic displays: Every floating text is an entity that updates constantly
- Poorly configured economy plugins: Database queries every tick will wreck you
- Laggy anti-cheat plugins: Some check every player action multiple times per second
- Excessive world edit operations: Limit who can use large selections
Install Spark and run /spark profiler start for 2-3 minutes during normal gameplay. The report will show exactly which plugins are causing problems.
Essential Performance Plugins
- FarmControl: Limits entities in farm areas
- ClearLag: Removes ground items periodically (configure carefully)
- EntityTrackerFixer: Optimizes entity tracking
- Spark: For performance profiling
Database and Storage Optimization
Your server’s storage speed directly impacts performance, especially during world saves and player logins.
Use an SSD—this isn’t optional anymore. NVMe drives are ideal, but any SSD beats mechanical drives by orders of magnitude for Minecraft.
Adjust auto-save interval in bukkit.yml:
ticks-per.autosave: 12000
This changes auto-save from every 5 minutes (6000 ticks) to every 10 minutes. Saving causes brief lag spikes, so reducing frequency helps.
Enable async chunk loading in Paper’s paper-global.yml—it’s usually enabled by default but worth verifying.
Network and Connection Optimization
Even a perfectly optimized server feels laggy if network settings are wrong.
netty-threads in server.properties should typically be 4 for most servers. Higher isn’t always better.
network-compression-threshold set to 256 balances CPU usage and bandwidth. Lower values use more CPU but less bandwidth.
Consider using a proxy like Velocity or BungeeCord if you’re running multiple servers. They handle connections more efficiently than having players connect directly to each server.
Monitoring and Maintenance
Performance optimization isn’t a one-time thing. Regular monitoring catches problems before players complain.
Use Spark for ongoing profiling. Run /spark tps to see current server performance. Anything consistently below 19.5 TPS needs investigation.
Check your timings report regularly: /spark profiler generates detailed reports showing exactly what’s consuming resources.
Restart your server daily. Memory leaks are real, and a scheduled restart (during off-peak hours) prevents performance degradation.
Frequently Asked Questions
How much RAM does a Minecraft 1.21.1 server actually need?
For vanilla survival with 10-15 players, 4-6GB is sufficient. Heavily modded servers or those with 30+ players need 8-12GB. More than 16GB rarely helps unless you’re running an enormous modded server with 100+ players.
Why does my server lag when players explore new chunks?
Chunk generation is CPU-intensive. Pre-generate your world using Chunky before opening to players, and set a world border to prevent forced generation during gameplay.
Should I use Paper or Purpur for best performance?
Both offer excellent performance. Paper is more conservative and stable. Purpur adds more configuration options and slightly more aggressive optimizations. For most servers, Paper is the safer choice; use Purpur if you want maximum control.
Can I optimize a server without restarting it?
Some changes (like plugin configs) can be reloaded, but JVM arguments and server.properties changes require a restart. Schedule restarts during low-traffic periods to apply optimizations.
What’s the biggest performance improvement I can make right now?
Switch from vanilla to Paper if you haven’t already. It’s a 5-minute change that typically doubles or triples performance immediately. Second biggest: reduce simulation distance to 4-6 chunks.
Final Thoughts
Server optimization isn’t about implementing every possible tweak—it’s about identifying your specific bottlenecks and addressing them systematically. Start with the big wins: proper JVM flags, Paper or Purpur server software, reduced view/simulation distances, and world pre-generation. Profile with Spark to find problem plugins. Most servers can achieve smooth 20 TPS with these fundamentals in place.
The best optimization is the one your players never notice—because everything just works.
