Why Arch Linux Switched Its Default Package Compression to Zstandard (zstd)
Arch Linux maintainers replaced the single‑threaded xz compression in devtools with Facebook's fast, multithreaded Zstandard algorithm at level ‑18, achieving dramatically higher compression and decompression speeds and more stable parallel processing, which will speed up pacman package installations.
Background
Arch Linux developers evaluated several compression algorithms for the devtools package build pipeline. The existing default command xz -c -z - is single‑threaded and slow; although a multithreaded version of xz exists, it has shown reliability problems in edge cases.
Chosen algorithm
They selected Zstandard (zstd), a fast lossless compression algorithm originally developed by Facebook. Zstd provides real‑time compression speeds comparable to or better than zlib while achieving higher compression ratios. It supports native multithreading.
Configuration and performance
Extensive benchmarking identified compression level -18 as the best trade‑off for Arch’s use case. The recommended command is:
zstd -c -T0 -18 -Compared with the previous xz -c -z -, this configuration offers:
Much higher compression speed
Much higher decompression speed – directly reducing pacman package installation time.
Stable, repeatable multithreaded operation without the reliability issues observed in multithreaded xz.
Integration status
The zstd implementation has been merged into the main Arch Linux development branch and is awaiting an official release. For full details see the Arch Linux developer mailing list announcement:
https://lists.archlinux.org/pipermail/arch-dev-public/2019-March/029520.html
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