Re: Adding LZ4 compression support to Btrfs

[Filipe Manana <fdmanana@gmail.com>]

On Thu, Feb 25, 2021 at 1:23 PM Neal Gompa <ngompa13@gmail.com> wrote:
>
> 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.

This has been brought up over and over for many years:

https://btrfs.wiki.kernel.org/index.php/FAQ#Will_btrfs_support_LZ4.3F

Things have to be evaluated in btrfs' context, i.e. how it uses compression.
More details there anyway.

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



-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”