branch master updated: posts: New post about sunsetting the gzip substitutes.

[Maxim Cournoyer]

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commit d4b73e1ee0a2677dcf468f505123cd47e8943bba
Author: Maxim Cournoyer <maxim.cournoyer@gmail.com>
AuthorDate: Tue Feb 8 22:54:05 2022 -0500

    posts: New post about sunsetting the gzip substitutes.
    
    * website/posts/gzip-substitutes-begone.md: New file.
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+title: Sunsetting gzip substitutes availability
+date: 2022-02-09 9:00
+author: Maxim Cournoyer
+tags: Build farm
+---
+
+Starting next month (2022/03/01), the build farm known as
+[ci.guix.gnu.org](https://ci.guix.gnu.org/) will no longer offer
+gzip-compressed binary substitutes. The Guix daemon has known to use
+lzip for substitutes [since
+2019](https://git.savannah.gnu.org/cgit/guix.git/commit/?id=66229b04ae0ee05779b93d77900a062b8e0e8770);
+unless you are running a very outdated daemon, you have no need to
+worry about this change.
+
+This idea was first discussed about a year ago, when it was found that
+gzip-compressed substitutes [accounted for about only 1% of the
+downloaded
+substitutes](https://lists.gnu.org/archive/html/guix-devel/2021-03/msg00333.html).
+Since then, the daemon [has gained support for
+zstd](https://git.savannah.gnu.org/cgit/guix.git/commit/?id=016299d85935cb269ae74c206c245ce23796160e)
+on top of gzip and lzip, and the build farm has happily generated
+compressed substitutes for all of these compression schemes.
+
+While migrating the storage array of the Berlin-hosted build farm to
+faster electronic storage, it was discovered that the cached
+substitutes use about 16 TiB of storage space, which means they occupy
+most of the new 22 TiB array, of which gzip substitutes account for
+6.5 TiB:
+
+```
+$ du -sh /var/cache/guix/publish/{gzip,lzip,zstd}
+6.5T    /var/cache/guix/publish/gzip
+4.8T    /var/cache/guix/publish/lzip
+4.0T    /var/cache/guix/publish/zstd
+```
+
+Letting go of gzip substitutes will allow such storage space to be
+re-purposed to more pressing needs (such as a growing `/gnu/store`).
+In the future, we may consider offering only zstd-compressed
+substitutes, as zstd offers a competitive compression ratio compared
+to lzip (as can be glimpsed above) while being faster to both compress
+and decompress.