Re: apply different compress/compress-force settings on different subvolumes ?

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2024/2/21 19:19, Roland 写道:
> hello,
>
> what can be the reason , that multiple compress mount option do not work
> on subvolume level , i.e. it's always the first that wins ?

In that case, you may want to use "btrfs prop" subcommand to setup
compression for each subvolume.

The mount option one is really affecting the whole filesystem.

>
> and why is compress-force silently ignored? (see below)

Compress-force has no coresponding per-inode prop option though.

But I don't think compress-force would cause much difference against
regular compress.

>
> regarding compress mount option, it seems that this can be overriden via
> subvolume property, which can work around the problem and have multiple
> compression settings.
>
> but how to fix compress-force in the same way, i.e. how can we have
> differenty compress-force settings with one btrfs fs ?
>
> wouldn't it make sense to introduce compress-force property for this ?
>
> what about replacing compress with compress-force (i.e. make it the
> default), as there is not much overhead with modern/fast cpu ?
>
> i think compress-force / compress is VERY confusing from and end user
> perspective - and even worse, i have set "compress" on a subvolume used
> for virtual machines and they do not get compressed at all (not a single
> bit) . so i think, compress option is pretty short-sighted and not, what
> an average user would expect (
> https://marc.info/?l=linux-btrfs&m=154523409314147&w=2 )

IIRC compress prop needs to be set to all inodes.
If you set it on a directory, only new inodes would inherit the prop,
the existing ones won't get the new prop.

Thanks,
Qu
>
> i'd be happy on some feedback. not subscribed to this list, so please CC.
>
> roland
>
>
> zstd compression applied to all subvolumes, though specified otherwise:
>
> cat /etc/fstab|grep btrfs
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/zstd btrfs
> subvol=zstd,compress=zstd,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/lzo  btrfs
> subvol=lzo,compress=lzo,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/none btrfs
> subvol=none,compress=none,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/zstd-force btrfs
> subvol=zstd-force,compress-force=zstd,defaults 0 1
>
> mount|grep btrfs
> /dev/sdb1 on /btrfs/zstd type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=259,subvol=/zstd)
> /dev/sdb1 on /btrfs/lzo type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=257,subvol=/lzo)
> /dev/sdb1 on /btrfs/none type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=258,subvol=/none)
> /dev/sdb1 on /btrfs/zstd-force type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=260,subvol=/zstd-force)
>
>
> different order in fstab has different result - first wins:
>
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/lzo  btrfs
> subvol=lzo,compress=lzo,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/zstd btrfs
> subvol=zstd,compress=zstd,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/none btrfs
> subvol=none,compress=none,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/zstd-force btrfs
> subvol=zstd-force,compress-force=zstd,defaults 0 1
>
> /dev/sdb1 on /btrfs/lzo type btrfs
> (rw,relatime,compress=lzo,ssd,discard=async,space_cache=v2,subvolid=257,subvol=/lzo)
> /dev/sdb1 on /btrfs/zstd type btrfs
> (rw,relatime,compress=lzo,ssd,discard=async,space_cache=v2,subvolid=259,subvol=/zstd)
> /dev/sdb1 on /btrfs/none type btrfs
> (rw,relatime,compress=lzo,ssd,discard=async,space_cache=v2,subvolid=258,subvol=/none)
> /dev/sdb1 on /btrfs/zstd-force type btrfs
> (rw,relatime,compress=lzo,ssd,discard=async,space_cache=v2,subvolid=260,subvol=/zstd-force)
>
>
> compress-force silently ignored:
>
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/zstd btrfs
> subvol=zstd,compress=zstd,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/lzo  btrfs
> subvol=lzo,compress=lzo,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/none btrfs
> subvol=none,compress=none,defaults 0 1
> UUID=da0fadf1-5db4-4f5b-a77e-2f0730f4e872 /btrfs/zstd-force btrfs
> subvol=zstd-force,compress-force=zstd,defaults 0 1
>
> /dev/sdb1 on /btrfs/zstd type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=259,subvol=/zstd)
> /dev/sdb1 on /btrfs/lzo type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=257,subvol=/lzo)
> /dev/sdb1 on /btrfs/none type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=258,subvol=/none)
> /dev/sdb1 on /btrfs/zstd-force type btrfs
> (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=260,subvol=/zstd-force)
>
>
>
> this is the write speed i get with compress-force=zstd on i7-7700
>
> # dd if=/dev/zero of=test.dat bs=1024k count=10240 ;time sync
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB, 10 GiB) copied, 3.76111 s, 2.9 GB/s
>
> real    0m0.224s
> user    0m0.000s
> sys    0m0.081s
>
>
>