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Date:   Thu, 25 Feb 2021 10:50:56 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     dsterba@suse.cz, Neal Gompa <ngompa13@gmail.com>,
        Amy Parker <enbyamy@gmail.com>,
        Btrfs BTRFS <linux-btrfs@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: Adding LZ4 compression support to Btrfs
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On Thu, Feb 25, 2021 at 02:26:47PM +0100, David Sterba wrote:
> 
> LZ4 support has been asked for so many times that it has it's own FAQ
> entry:
> https://btrfs.wiki.kernel.org/index.php/FAQ#Will_btrfs_support_LZ4.3F
> 
> The decompression speed is not the only thing that should be evaluated,
> the way compression works in btrfs (in 4k blocks) does not allow good
> compression ratios and overall LZ4 does not do much better than LZO. So
> this is not worth the additional costs of compatibility. With ZSTD we
> got the high compression and recently there have been added real-time
> compression levels that we'll use in btrfs eventually.

When ZSTD support was being added to btrfs, it was claimed that btrfs compresses
up to 128KB at a time
(https://lore.kernel.org/r/5a7c09dd-3415-0c00-c0f2-a605a0656499@fb.com).
So which is it -- 4KB or 128KB?

- Eric