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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

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2 Answers 2

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16

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.

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  • 2
    That's terribly slow, though. Commented Jan 27, 2024 at 13:44
  • 1
    It is, but is there a faster way? Commented Feb 6, 2024 at 15:17
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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
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  • Be very careful with enabling quotas - serious performance degradation on snapshot heavy filesystems is found with a quick search. Commented Apr 26 at 11:18

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