Re: [question] free space of disk with btrfs is too different from other du

[Su Yue <l@damenly.su>]

On Tue 22 Jun 2021 at 21:02, 吴振宇 <wuzy001@gmail.com> wrote:

> Sorry for my disturbance!
>
> my disk with btrfs filesystem tell me it doesn't have enough 
> free space:
>
> ```
> $ sudo btrfs fi df /
> Data, single: total=448.02GiB, used=427.74GiB
> System, DUP: total=8.00MiB, used=64.00KiB
> Metadata, DUP: total=8.80GiB, used=6.39GiB
> GlobalReserve, single: total=512.00MiB, used=0.00B
> $ sudo btrfs fi usage /
> Overall:
>     Device size:                 465.64GiB
>     Device allocated:            465.63GiB
>     Device unallocated:            1.00MiB
>     Device missing:                  0.00B
>     Used:                        440.54GiB
>     Free (estimated):             20.26GiB      (min: 20.26GiB)
>     Data ratio:                       1.00
>     Metadata ratio:                   2.00
>     Global reserve:              512.00MiB      (used: 0.00B)
>     Multiple profiles:                  no
>
> Data,single: Size:448.02GiB, Used:427.76GiB (95.48%)
>    /dev/sda2     448.02GiB
>
> Metadata,DUP: Size:8.80GiB, Used:6.39GiB (72.60%)
>    /dev/sda2      17.60GiB
>
> System,DUP: Size:8.00MiB, Used:64.00KiB (0.78%)
>    /dev/sda2      16.00MiB
>
> Unallocated:
>    /dev/sda2       1.00MiB
> $ sudo btrfs fi show /
> Label: none  uuid: 644a9e91-5e05-4f5d-a79b-e0eccd21a1a8
>         Total devices 1 FS bytes used 434.14GiB
>         devid    1 size 465.64GiB used 465.63GiB path /dev/sda2
>
> $ df -Th
> Filesystem     Type      Size  Used Avail Use% Mounted on
> devtmpfs       devtmpfs  3.8G     0  3.8G   0% /dev
> tmpfs          tmpfs     3.9G   46M  3.8G   2% /dev/shm
> tmpfs          tmpfs     3.9G  3.9M  3.9G   1% /run
> /dev/sda2      btrfs     466G  442G   21G  96% /
> tmpfs          tmpfs     3.9G  204K  3.9G   1% /tmp
> /dev/sda1      vfat      128M  125M  2.9M  98% /boot
> tmpfs          tmpfs     785M   16K  785M   1% /run/user/994
> tmpfs          tmpfs     785M   80K  785M   1% /run/user/1000
> ```
>
> however, i try to use gdu to scan my disk. it tell me
>
> ```
> $ sudo gdu /
>  gdu ~ Use arrow keys to navigate, press ? for help
>  --- / ---
>    49.9 GiB [#####     ] /usr
>    15.1 GiB [#         ] /home
>    11.1 GiB [#         ] /opt
>     6.5 GiB [          ] /var
>   930.8 MiB [          ] /lib
>   124.9 MiB [          ] /boot
>    55.2 MiB [          ] /root
>    50.6 MiB [          ] /etc
>    27.1 MiB [          ] /sbin
>    23.5 MiB [          ] /lib64
>    10.9 MiB [          ] /bin
> . 312.0 KiB [          ] /tmp
>    20.0 KiB [          ] /mnt
> e   4.0 KiB [          ] /srv
> e   4.0 KiB [          ] /tftproot
> @   4.0 KiB [          ] media
>  Total disk usage: 83.8 GiB Apparent size: 78.4 GiB Items: 
>  2424046
> Sorting by: size desc
> ```
>
> 427.76GiB or 83.8 GiB!
>
Maybe your fs have some snapshots?
Try:

btrfs subvolume list /

--
Su

> i know btrfs is a CoW filesystem, which means it will cost more 
> space
> to store a file. but the gap is too large, which it is hard to 
> accept
> the fact.
> who can tell me what happened to my disk? and how can i do to 
> rescue
> my hard disk? the rest free space is not enough. if i cannot 
> find the
> solution, maybe i should format my hard disk to get more free 
> space.
> thanks.
>
> there are some information which maybe useful.
>
> ```
> $ uname -r
> 5.11.7-gentoo-x86_64
> $ btrfs --version
> btrfs-progs v5.9
> $ dmesg > dmesg.txt && wgetpaste -s dpaste dmesg.txt
> Pasting > 25 kB often tend to fail with dpaste. Use --verbose or
> --debug to see the
> error output from wget if it fails. Alternatively use another 
> pastebin service.
> Your paste can be seen here: https://dpaste.com/FCZF83YYA
> ```