Why isn't my free space increasing after deleting files on BTRFS?
June 7, 20256 answers
Asked byCuriousCoder72
I'm using Ubuntu 25 with the BTRFS file system and recently cleared out a ton of space by deleting large `~/.cache` folders (around 20GB each for two users). After doing this and restarting my system, I expected to see the available space increase, but it actually decreased from about 45GB to 33GB. I've checked that the Trash is empty and there's only about 100MB in `/tmp`. When I used `Filelight`, it accurately showed much less data in my home folders now, but when I ran `btrfs filesystem df /`, the output still indicates that most of my space is used up. So I'm curious, where did my free space go?
When you're using BTRFS, it employs a copy-on-write (CoW) feature that can cause a delay in updating the free space displayed. Even after you've deleted files, the disk space reports might not reflect this change right away because of how the file system operates. It’s worth waiting a bit and checking back later.
FileNinja89: Would running the `sync` command help clear up the space? I’m unsure, but maybe that would trigger the update.
DataDude42: I thought CoW and snapshots were supposed to be transparent for users. Why isn't the deleted space being reported like it would be on other systems?
Reply to this answerLinuxGuru123
For BTRFS, skip the usual `df` and `du` commands; try using `btrfs filesystem usage /` or `btrfs filesystem df /` instead. They provide more accurate info on what’s actually happening with your disk space.
CuriousCoder72: I checked `btrfs filesystem df /`, and it still doesn't show additional space. Shouldn't all these features be seamless for the user? I removed some old snaps too, but no changes are showing.
OldBTRFSUser: Exactly, those features should ideally be invisible, just like on other platforms. It's frustrating when you’re not seeing the expected free space.
Reply to this answerSnapshotSleuth
Have you checked if there are any BTRFS snapshots still holding onto the space you thought you freed? Sometimes old snapshots can retain deleted files, affecting the available space you've freed up.
Reply to this answerDataDude42
I’ve seen similar issues before. It could be that the snapshots you've mentioned are still tied to the data you deleted. Even if they’re old, the data might still count against your used space.
SnapshotSleuth: You're right, the age of snapshots doesn't matter. What counts is whether they still contain data that should have been cleared.
Reply to this answerBTRFSNoob
I had a bad experience with BTRFS years ago; my system got corrupted without any odd behaviors on my part. I switched to ZFS and haven’t had issues since. BTRFS seems to have improved, though, since it’s the default in some distros now.
VeteranUser99: I’ve used BTRFS since 2013 on various systems and never lost data due to the file system itself. I think a lot of the issues come down to edge cases or user error. Just to clarify, Arch doesn’t have a default filesystem, right?
Reply to this answerTechSavvy246
Different setups might yield different experiences. It’s becoming standard in distributions like OpenSuse or on NAS devices, which suggests it’s reliable, but still, user experiences can vary.
FileNinja89: Would running the `sync` command help clear up the space? I’m unsure, but maybe that would trigger the update.
DataDude42: I thought CoW and snapshots were supposed to be transparent for users. Why isn't the deleted space being reported like it would be on other systems?