Your Minecraft server ran out of disk space: find the cause and make room

How a full disk shows itself

A Minecraft server writes to disk all the time: terrain that changed, player inventories, statistics, the log. When there is no room left, those writes fail, and the server says so in the console with lines like these:

java.io.IOException: No space left on device
Failed to save chunk 12,-4
Failed to store chunk
Failed to save player data for Kai
Couldn't save stats to world/players/stats/<uuid>.json
Failed to save level world
Unable to save the game (is there enough disk space?)

That last row is the plan limit rather than a physical disk. The disk use of a server is measured while it runs, and once the server folder is larger than the disk your plan comes with, the server is stopped and a new start is refused until the folder fits again.

See how full the disk really is

The Storage card on the Overview tab shows how much the server folder uses next to the disk of your plan, with the share in percent below it. The number is measured at intervals rather than on every write, so right after a big delete it can take a little while before it drops.

The Files tab tells you where that space went, with one catch: its Size column only gives a number for files. A folder shows a dash, however much is inside. So you work downwards: open a folder, read the sizes of the files in it, and move on to the next.

1. 1

   Look at the top of the server folder first

   Loose .zip and .tar.gz files sit right there, and they are the easiest space to win back.

2. 2

   Open logs and crash-reports

   Look at the dated archives in logs and the reports in crash-reports.

3. 3

   Open the plugin and mod folders

   Look inside plugins, and for folders such as bluemap or mods-oud-20260914 at the top.

4. 4

   Look at the world last

   On 26.1 and newer the overworld terrain is in world/dimensions/minecraft/overworld/region, as .mca files. Many large region files mean the world itself is the heavy part.

What usually fills a server

The world is the one that surprises people. Its size depends on how much land has been explored, not on how long anyone has played. A single player who flies out with an elytra in a straight line for an evening can add more terrain than a month of building at spawn.

What is safe to delete, and what never is

Plugin data that grows in the background

The CoreProtect block log

CoreProtect writes a record for every change to the world, which is exactly what makes a rollback possible, and exactly why its database grows on a busy server. New installations keep it in plugins/CoreProtect/database.duckdb. Deleting that file wipes the whole history, so trim it with a purge instead:

co purge t:30d

This removes everything older than thirty days. In the game, a purge refuses anything shorter than 30 days; from the console it accepts periods down to 24 hours. After a purge you can no longer roll back changes from before that point, so pick a period that still covers the griefs people report late. To keep the log smaller from now on, a blacklist.txt in the CoreProtect folder stops logging for the users, blocks or commands you list. How the log is used for rollbacks is in the guide to stopping griefing.

Map tiles from BlueMap

BlueMap stores its rendered maps as compressed tiles in bluemap/web/maps, one folder per map. A map of a world nobody looks at, such as the Nether on a server where the web map is only used for the overworld, is space you can win back:

bluemap freeze <map>
bluemap purge <map>

bluemap purge deletes all rendered data of that map, and BlueMap draws it again from scratch unless the map is frozen. That is why the freeze comes first: it pauses updates on that map, and the pause survives a restart.

Keep the world from growing without end

Clearing logs buys you weeks. A world without an edge keeps growing for as long as players keep exploring, so the lasting fix is to decide how big it may get.

• Set a world border. Players cannot travel past it, so no new terrain is created beyond it. The pre-generation guide shows the two commands and how wide to make it.
• Pre-generate inside that border. The pre-generate card on the World tab shows how much disk space each radius will take before you start, and marks a radius that does not fit on your disk. Generated land takes its space up front, but after that the world stops growing.
• Give a worn out dimension a fresh start. A Nether that players have flown through for a year can be deleted on its own and comes back new, which is covered in the guide to resetting the Nether or the End.
• Clear logs and crash reports now and then. Nothing on the server removes them for you.

How backups relate to the disk of your plan

Backups on the Backups tab are not kept in your server folder. They do not show up on the Files tab and they do not count toward the Storage card, so making one does not push a nearly full server over its limit, and deleting one does not give the server any room.

They have a limit of their own. On plans with backup slots, the Backups tab shows how much space your backups take of the room your plan has for them. Close to that limit you may keep fewer backups than you have slots, so lock the ones you would want back. A plan without backup slots says so on that tab.

Copies you make yourself are different. A world zipped on the Files tab, a folder copied under another name or a backup folder written by a plugin all sit in the server folder and count toward the Storage card.

Checking after a clean-up

1. 1

   Watch the Storage card

   Give it a little while to measure again. The server needs clear headroom below the plan disk, not just a few megabytes, because the world keeps writing as soon as it starts.

2. 2

   Start the server and read the console

   Let it load fully and search the console for Failed to save and No space left. Neither should appear.

3. 3

   Save once by hand

   Run save-all in the console. Saved the game means the server can write to disk again; Unable to save the game means it still cannot.

4. 4

   Join and check the last session

   Check the builds from the evening the disk filled up, and ask players to check their inventories. What failed to save is missing, and only a backup from before that evening brings it back.

If the server will not start at all after a full disk, the guide to a server that will not start covers a damaged level.dat, and reading crash reports and logs helps with the rest.