[Solved] Used Space for Cache Drive - Conflicting Reporting and ghost files

[eep]

Edit: see my reply, ran defrag and space was re-allocated.

 

I am having the same problem others have had that I am linking to below, although there didn't seem to be a known solution. I tried invoking Mover, scrub, and Check Filesystem Status in maintenance mode and it found no errors. I have 60GB of files on the cache drive according to dolphin and the du command but 97GB is being used as reported by btrfs and the GUI. I suspect this is "ghost" files from Unraid crashing while files were open but how do I find/delete those?

root@Server:/mnt# du -sh /mnt/cachetwo
60G     /mnt/cachetwo
root@Server:/mnt# btrfs fi df -H /mnt/cachetwo
Data, RAID1: total=117.85GB, used=96.96GB
System, RAID1: total=33.55MB, used=16.38kB
Metadata, RAID1: total=2.15GB, used=437.42MB
GlobalReserve, single: total=256.61MB, used=0.00B

 

 

 

 

Edited March 11, 2022 by eep
resolved

[JorgeB]

2 minutes ago, eep said:

used=96.96GB

du (and other tools) isn't reliable with btrfs, this will be the actual used space.

[eep]

But I am seeing 60GB of files in Samba and in Dolphin when browsing the Cache drive (including showing hidden folders). How do I see exactly whats taking up the space? I could be symlinks but not sure.

[JorgeB]

If you can't see start moving the data outside the pool, to the array for example, vdisks are a usual suspect, they can expand if not trimmed.

[eep]

Thanks for replying Jorge, while that didn't help it did motivate me to find a solution. I knew it had to be corruption form an unclean shutdown.

Ran defrag and it cleared up all the "unused" space.  BTW I was able to run defrag while my VM and dockers were live!

btrfs filesystem defragment -rvf /mnt/cachetwo

See discussion below, this seems like a big issue with BTRFS, I hope there is an alternative soon for RAID1 cache. Luckily, Unraid does not use snapshots by default so no issues with defrag adding used space.

 

[JorgeB]

Trimming the images/vdisks should have the same result.