Hi, I have read a lot of caveats about interpreting the free space reported for btrfs volumes, but could not find anything about the perceived inconsistency in the disk usage reporting described below.
I have a btrfs volume with about 135GiB used for data, as reported by `df`, `btrfs fi show` and `btrfs fi usage` alike: # btrfs filesystem show /volumes/main/ Label: 'main' uuid: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx Total devices 1 FS bytes used 134.12GiB devid 1 size 193.43GiB used 165.01GiB path /dev/sda2 However, `btrfs fi du` reports ~17GiB exclusive usage and ~80GiB shared usage, which adds up to only 97GiB (compared to the 135GiB I would expect): # btrfs filesystem du -s /volumes/main/ Total Exclusive Set shared Filename 1.73TiB 17.20GiB 80.13GiB /volumes/main/ (The reported total usage exceeding the disk capacity by an order of magnitude is expected as the volume contains many snapshots.) The mount point corresponds to the root subvolume, thus all subvolumes should be accounted for by `btrfs fi du` (according to its documentation): # mount | grep /volumes/main /dev/sda2 on /volumes/main type btrfs (rw,noatime,ssd,space_cache,autodefrag,subvolid=5,subvol=/) Do I misunderstand the meaning of exclusive and shared usage or is there some other issue causing this behaviour? I would expect the disk usage reported by `df`, `btrfs fi show` and `btrfs fi usage` to be the sum of the exclusive and shared usage reported by `btrfs fi du`. The output of `btrfs fi usage`, for completeness's sake: # btrfs filesystem usage /volumes/main/ Overall: Device size: 193.43GiB Device allocated: 165.01GiB Device unallocated: 28.41GiB Device missing: 0.00B Used: 134.12GiB Free (estimated): 57.00GiB (min: 57.00GiB) Data ratio: 1.00 Metadata ratio: 1.00 Global reserve: 194.72MiB (used: 0.00B) Data,single: Size:162.00GiB, Used:133.41GiB (82.35%) /dev/sda2 162.00GiB Metadata,single: Size:3.01GiB, Used:720.88MiB (23.41%) /dev/sda2 3.01GiB System,single: Size:4.00MiB, Used:48.00KiB (1.17%) /dev/sda2 4.00MiB Unallocated: /dev/sda2 28.41GiB Thanks, Zoltan