BTRFS Housekeeping?

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1

I’m wondering if there is any “house keeping” to be done if you have BTRFS as your file system. I currently have it installed (Manjaro KDE) and I noticed that deleting files is slow (not how it used to be). I have a decent SSD for anyone wondering. I noticed the same slowness on my laptop (Also Manjaro KDE). I’m wondering if this has to do with BTRFS or if it’s something else?

2

It is probably caused by something else, unless you have the filesystem mounted with the sync option, and/or with the discard option. Check your /etc/fstab for those two mount options, and if they are present, remove them.

Rationale:

  • discard is deprecated. Enabling the fstrim.timer is much better.

  • The default mount options for filesystems on an SSD or an HDD include async, which buffers the writes. This is much more efficient than sync, which immediately commits all write operations to the drive.

3

Here is what I have in my fstab

# <file system>             <mount point>  <type>  <options>  <dump>  <pass>
UUID=A077-8C9B                            /boot/efi      vfat    umask=0077 0 2
UUID=1949a224-fc40-4844-9b85-9bac441667b0 /              btrfs   subvol=@,defaults,noatime,space_cache 0 1
UUID=1949a224-fc40-4844-9b85-9bac441667b0 /home          btrfs   subvol=@home,defaults,noatime,space_cache 0 2
UUID=34bde0d2-cd72-49fd-8d42-585fce212fbf swap           swap    defaults,noatime 0 0
/dev/sdb1 /Media/D auto nosuid,nodev,nofail,x-gvfs-show 0 0

To make sure, you saying to add fstrim.timer and async to the options for the btrfs partitions?

4

No, not at all. async is already in effect ─ it is part of the defaults ─ and fstrim.timer isn’t a mount option; it’s a systemd timer. Chances are that it’s already running on your system. You can easily check that… :arrow_down:

[nx-74205:/dev/pts/3][/home/aragorn]
[04:17:29][aragorn] >  systemctl status fstrim.timer
● fstrim.timer - Discard unused blocks once a week
     Loaded: loaded (/usr/lib/systemd/system/fstrim.timer; enabled; vendor preset: disabled)
     Active: active (waiting) since Wed 2022-01-12 19:59:42 CET; 4 days ago
      Until: Wed 2022-01-12 19:59:42 CET; 4 days ago
    Trigger: Mon 2022-01-24 01:23:28 CET; 6 days left
   Triggers: ● fstrim.service
       Docs: man:fstrim

Jan 12 19:59:42 nx-74205 systemd[1]: Started Discard unused blocks once a week.

[nx-74205:/dev/pts/3][/home/aragorn]
[04:17:42][aragorn] >

Note: If it’s not running, start it as follows… :arrow_down:

sudo systemctl enable --now fstrim.timer

But that all said, I don’t see any immediate reason as to why you report that your system is slow at deleting files. :man_shrugging:

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5

On a side note, you really shouldn’t mount this with this type of identifier, this is unreliable, as the other mounts, use the UUID instead of /dev/sdb1

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7

I suggest to remove space_cache :sunglasses:

Please have a look at

https://btrfs.readthedocs.io/en/latest/Administration.html

And an aditional Question:

  • Do you use snapshots?
  • How many ?
  • Do you clean them up ?

Please provide:

sudo sudo btrfs device usage /

Btrfs

https://wiki.manjaro.org/index.php/Btrfs

8

Thank you and everyone else for the suggestions I will apply them. I do have fstrim.timer running in systemd.
I have 6 snapshots. If by clean you mean delete old ones, yes. I just reduced it to 2 snapshots.

here is the paste:

/dev/nvme0n1p2, ID: 1
   Device size:           228.39GiB
   Device slack:              0.00B
   Data,single:           139.01GiB
   Metadata,single:         5.01GiB
   System,single:           4.00MiB
   Unallocated:            84.38GiB
9

I do have 60 Snapshots of / and 40 of /home and my Unallocated is at 50% :wink:

When keeping snapshots, you have to watch closely this value. It should never go under 10% of your device size

When you got under 10% (accidentally), an balance (once) may improve performance. But before balancing it is good to get over 10%

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