BTRFS compression not enabled by default?

umaxtu · October 8, 2021, 3:06pm

When I installed Endeavour, I chose the erase entire disk and BTRFS options. But later when I installed compsize to check how effective the compression was, the output didin’t seem to indicate that there was any compression in use (I did a stupid and forgot to record the output before I went and changed things).

After running sudo btrfs filesystem defragment -rvf -czstd / the output of compzise now shows compression being enabled using zstd.

So assuming that I’m interpreting things correctly and my btrfs filesystem doesn’t have compression enabled, I can change that by adding compression to the options in /etc/fstab for each subvolume correct?

Thank you in advance.

dalto · October 8, 2021, 3:10pm

I would recommend adding compress=zstd

joekamprad · October 8, 2021, 3:11pm

welcome at the purple side

I am still not that comfortable with BTRFS but choosing the preset scheme and automatic partition you should have compression:

and @dalto

already changed it to zstd for compression for the next release

dalto · October 8, 2021, 3:12pm

It has been a while since I looked at it the current fstab.conf but it used to only add compress if it detected an ssd. Has that changed?

joekamprad · October 8, 2021, 3:14pm

oh yes this could be still the case, I do not test BTRFS so much only current using it here on one hardware install…

pebcak · October 8, 2021, 3:22pm

Also, is it possible to set fs passno to 0 ?

Traditional filesystems need to run their respective fsck utility in case the filesystem was not unmounted cleanly and the log needs to be replayed before mount. This is not needed for btrfs. You should set fs_passno to 0.

https://btrfs.wiki.kernel.org/index.php/FAQ#When_will_Btrfs_have_a_fsck_like_tool.3F

dalto · October 8, 2021, 3:46pm

@joekamprad this requires a really minor code change unless Garuda upstreamed their change.

If you want I can check and if not I can submit a PR for it against Calamares

umaxtu · October 8, 2021, 3:48pm

Interesting, I don’t have compress in my options at all.
Screenshot_20211008_114708

Adding compress=zstd now for /, /home, and /var/log (compressing swap and /var/cache don’t seem like good ideas to me).
And my drive is a nvme ssd in case that matters.

dalto · October 8, 2021, 4:05pm

It looks like this has been upstreamed in Calamares already:

pebcak · October 8, 2021, 4:07pm

Great!
Thanks for looking that up and sharing it here!

umaxtu · October 8, 2021, 4:09pm

Is that a change I should make in my existing installation’s fstab?

dalto · October 8, 2021, 4:12pm

You can if you want to. fsck.btrfs is a shell script which does more or less nothing so there is not much harm in calling it. However, there is also no benefit so might as well set it 0.

joekamprad · October 8, 2021, 4:14pm

@dalto

github.com

calamares/calamares/blob/132bca649e6f1f35a45c38ec10b840be6c5bb428/src/modules/fstab/fstab.conf#L16

    
      
          #
          # When creating fstab entries for a filesystem, this module
          # uses the options for the filesystem type to write to the
          # options field of the file.
          ---
          # Mount options to use for all filesystems. If a specific filesystem
          # is listed here, use those options, otherwise use the *default*
          # options from this mapping.
          mountOptions:
              default: defaults,noatime
              btrfs: defaults,noatime,space_cache,autodefrag,compress=zstd
          
          
# Mount options to use for the EFI System Partition. If not defined, the
          # *mountOptions* for *vfat* are used, or if that is not set either,
          # *default* from *mountOptions*.
          efiMountOptions: umask=0077
          
          
# If a filesystem is on an SSD, add the following options. If a specific
          # filesystem is listed here, use those options, otherwise no additional
          # options are set (i.e. there is no *default* like in *mountOptions*).
          #

as there is also the extra SSD options part it seems to be use compression not only for SSD:

github.com

calamares/calamares/blob/132bca649e6f1f35a45c38ec10b840be6c5bb428/src/modules/fstab/fstab.conf#L34

    
      
          # filesystem is listed here, use those options, otherwise no additional
          # options are set (i.e. there is no *default* like in *mountOptions*).
          #
          # This example configuration applies the *discard* option to most
          # common filesystems on an SSD. This may not be the right option
          # for your distribution. If you use a systemd timer to trim the
          # SSD, it may interfere with the *discard* option. Opinions vary
          # as to whether *discard* is worth the effort -- it depends on
          # the usage pattern of the disk as well.
          #
          # ssdExtraMountOptions:
          #     ext4: discard
          #     jfs: discard
          #     xfs: discard
          #     swap: discard
          #     btrfs: discard,compress=lzo
          #
          # The standard configuration applies asynchronous discard support and ssd optimizations to btrfs
          # and does nothing for other filesystems.
          ssdExtraMountOptions:
              btrfs: discard=async,ssd

@pebcak as @dalto says fs_passno 0 Garuda dev commits this already…

dalto · October 8, 2021, 4:18pm

Yeah, it looks like the compression defaults changes were committed 2 weeks ago:

joekamprad · October 8, 2021, 4:20pm

BTRFS is still under heavy changes on calamares. Currently, I see Manjaro got issues with snapshot implementation… which will resulting in more changes to calamares soon.

Hopeful we will get a new release ready soon Currently, I struggle with a great merging of repos action on GitHub affecting also structure for the install process … but I am almost 2/3 through it

joekamprad · October 8, 2021, 4:26pm

It is so that current release do not have the latest calamares… so it will only put compression if ssd is used.