How to display btrfs snapshot size

Question

I have quite a lot of snapshot on some btrfs volume, an I would like to know how much each snapshot take as space, so I will know when and were there is important changes.

sudo btrfs subvolume show /home/
/
Name:           <FS_TREE>
UUID:           -
Parent UUID:        -
Received UUID:      -
Creation time:      -
Subvolume ID:       5
Generation:         1181373
Gen at creation:    0
Parent ID:      0
Top level ID:       0
Flags:          -
Snapshot(s):
            .snapshot/_0
            .snapshot/_1
            .snapshot/_2
            .snapshot/_3
            .snapshot/_4
            ...

but if I use du they report the whole space

du -sh /home/.snapshot/*
1,2T    /home/.snapshot/_0
1,2T    /home/.snapshot/_1
1,2T    /home/.snapshot/_2

is there a way to discover which difference is there, in space, between _1 and _2

Edit: NB : I have been using btrfs-list successfully to simply show snapshot size

Try sudo btrfs sub show /home/.snapshot/_0 instead. It should show usage stats at the end. — ajgringo619, Apr 14 '22 at 18:43
thanks @ajgringo619 , but it gives me same info as above. no usage stats — dominix, Apr 14 '22 at 22:07
How to check (simulate), how much space will be freed after I remove a btrfs subvolume? — Kamil Maciorowski, Apr 15 '22 at 00:29

score 9 · Accepted Answer · edited Mar 20 '23 at 13:57

Enabling quota is not a recommended if you have lot of backups.

Instead, you can use btrfs filesystem du -s command:

# btrfs filesystem du -s @snapshot*
     Total   Exclusive  Set shared  Filename
  17.98GiB    13.05GiB     4.93GiB  @snapshot_system_2022-01-22d
  17.91GiB     2.66GiB    15.25GiB  @snapshot_system_2023-01-22w
  18.09GiB     2.08GiB    16.01GiB  @snapshot_system_2023-01-29w
  16.90GiB     2.05GiB    14.85GiB  @snapshot_system_2023-02-05w
  18.23GiB     1.96GiB    16.27GiB  @snapshot_system_2023-02-12w
  18.81GiB     2.07GiB    16.74GiB  @snapshot_system_2023-02-19w
  21.59GiB     4.90GiB    16.69GiB  @snapshot_system_2023-02-26w
  22.38GiB   172.61MiB    22.21GiB  @snapshot_system_2023-03-18d

See man btrfs-filesystem or BTRFS docs.

That's terribly slow, though. – Auspex Jan 27 '24 at 13:44 — Auspex, Jan 27 '24 at 13:44
It is, but is there a faster way? – Jarppiko Feb 06 '24 at 15:17 — Jarppiko, Feb 06 '24 at 15:17

score 0 · Answer 2 · answered Apr 14 '22 at 22:56

In order to show usage data with your BTRFS subvolumes, you must enable quotas first, like this:

sudo btrfs quota enable /home

Then, you can run commands like sudo btrfs subvol show /home/.snapshots/your_snapshot and get usage stats. Here's an example:

    sudo btrfs subvol show /.snapshots/1076/snapshot/
@/.snapshots/1076/snapshot
    Name:           snapshot
    UUID:           3ba9ffa0-a355-d544-be10-1b1d0a3a321e
    Parent UUID:        5c0c4206-9b15-074f-83c3-65861366e318
    Received UUID:      -
    Creation time:      2022-02-01 00:00:09 -0800
    Subvolume ID:       1445
    Generation:         66371
    Gen at creation:    66370
    Parent ID:      275
    Top level ID:       275
    Flags:          readonly
    Send transid:       0
    Send time:      2022-02-01 00:00:09 -0800
    Receive transid:    0
    Receive time:       -
    Snapshot(s):
    Quota group:        0/1445
      Limit referenced: -
      Limit exclusive:  -
      Usage referenced: 13.92GiB
      Usage exclusive:  8.25GiB

How to display btrfs snapshot size

2 Answers2