On 28.03.2021 15:28, Zoltán wrote: > 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
It probably does not take in account exclusive usage of other subvolumes, likely snapshots. > 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 >
