Corrupted Chunk
The server errors on a chunk that appears to be claimed by another thread or partially written. A region file is damaged, and the affected chunk needs to be repaired or removed so it can regenerate.
What does this error mean?
Chunks are stored in region (.mca) files. When a chunk is half-written, usually after a crash during save, the server can hit a state where the chunk seems locked or invalid, and loading it fails.
Chunk is already taken by another thread
Most Common Causes
- A crash or kill during a chunk save.
- Concurrent writes to the same region file.
- Disk full while saving.
- Filesystem or disk errors.
- A mod writing malformed chunk data.
How To Diagnose
- Note the chunk/region coordinates from the log.
- Map the coordinates to the .mca file (region is 512x512 blocks).
- Back up the region file before touching it.
- Check disk health and free space.
Recommended Fixes
- Repair or delete in MCA Selector
Open the region and delete the broken chunk so it regenerates on next load. - Restore the region from backup
Swap the damaged .mca file for a recent backup to preserve builds. - Ensure single-writer access
Make sure only one process writes the world to avoid recurring damage. - Fix the disk
Free space and check the disk for errors to stop new corruption.
Frequently Asked Questions
Yes, anything in that chunk regenerates fresh. Restore from backup if the build matters.
Divide chunk coords by 32, the result names the r.X.Z.mca file.
Always stop cleanly, keep free disk space, and avoid two processes opening the same world.