Hi Pierre, The problem where using Btrfs compression wasn't effective for /gnu/store (or anything else) was caused by the init RAM disk not honoring options on the root file system.
I could notice about this when running just 'mount', and the options I gave in my config.scm were missing. Since this was fixed with commit 900ef20b1da66ad71145082c883dc12f31fafa54, retesting compsize gives better results :-). Here are the results when using the zstd compression (default level, 3) on the /gnu/store of this relatively new machine: --8<---------------cut here---------------start------------->8--- sudo compsize /gnu/store Password: Processed 1166359 files, 379224 regular extents (1025522 refs), 543008 inline. Type Perc Disk Usage Uncompressed Referenced TOTAL 65% 30G 46G 107G none 100% 23G 23G 52G zstd 29% 6.8G 22G 55G --8<---------------cut here---------------end--------------->8--- We see that there's 23 GiB that aren't compressed. I attribute those to already compressed files in the store, that Btrfs doesn't consider worth compressing. For the compressible files, Zstd achieves an impressive 29% compression ratio, while overall the compression ration is 65%. The last column shows how much space a traditional file system would need to store the content referenced. Maxim
