Re: Adding LZ4 compression support to Btrfs

[Neal Gompa <ngompa13@gmail.com>]

On Wed, Feb 24, 2021 at 11:10 PM Amy Parker <enbyamy@gmail.com> wrote:
>
> The compression options in Btrfs are great, and help save a ton of
> space on disk. Zstandard works extremely well for this, and is fairly
> fast. However, it can heavily reduce the speed of quick disks, does
> not work well on lower-end systems, and does not scale well across
> multiple cores. Zlib is even slower and worse on compression ratio,
> and LZO suffers on both the compression ratio and speed.
>
> I've been laying out my plans for a backup software recently, and
> stumbled upon LZ4. Tends to hover around LZO compression ratios.
> Performs better than Zstandard and LZO slightly for compression - but
> significantly outpaces them on decompression, which matters
> significantly more for users:
>
> zstd 1.4.5:
>  - ratio 2.884
>  - compression 500 MiB/s
>  - decompression 1.66 GiB/s
> zlib 1.2.11:
>  - ratio 2.743
>  - compression 90 MiB/s
>  - decompression 400 MiB/s
> lzo 2.10:
>  - ratio 2.106
>  - compression 690 MiB/s
>  - decompression 820 MiB/s
> lz4 1.9.2:
>  - ratio 2.101
>  - compression 740 MiB/s
>  - decompression 4.5 GiB/s
>
> LZ4's speeds are high enough to allow many applications which
> previously declined to use any compression due to speed to increase
> their possible space while keeping fast write and especially read
> access.
>
> What're thoughts like on adding something like LZ4 as a compression
> option in btrfs? Is it feasible given the current implementation of
> compression in btrfs?

This is definitely possible. I think the only reason lz4 isn't enabled
for Btrfs has been the lack of interest in it. I'd defer to some of
the kernel folks (I'm just a user and integrator myself), but I think
that's definitely worth having lz4 compression supported.



-- 
真実はいつも一つ！/ Always, there's only one truth!