On Sun, Jan 19, 2020 at 4:42 PM Bohdan Khomutskyi <bkhomuts@redhat.com> wrote:

Thanks everyone for posting feedback.
More benchmarking results are available at https://fedoraproject.org/wiki/Category:Changes/OptimizeSquashFS, including the 'plain' SquashFS filesystem.
After performing the tests, I personally recommend to use xz compression with 1MiB block size, without bcj, on a 'plain' squash filesystem -- this will lead to a reduction of 142MiB on the ISO, compared to the stock Fedora 31 Workstation x86_64 image.
Alternative compression options, such as Zstd, are also mentioned in the change proposal.

Hmm, and I see I've been completely confused in my last reply, and I considered the numbers in the first image [1] to be installation times. Instead they are image creation times. OK. Looking at the new second image [2], Zstd seems like a clear winner to me at least for QA purposes. With fine tuning the compression level, we can achieve almost the same file size for a great installation speedup.

[1] https://fedoraproject.org/wiki/File:Compression_vs_SquashFS_creation_time.png
[2] https://fedoraproject.org/wiki/File:Compression_vs_installation_time.png