The nix store in of itself should be highly compressible. Here's the output of "compsize -x /nix/store" on my BTRFS root with compress-force=zstd:6 Processed

The nix store in of itself should be highly compressible. Here's the output of "compsize -x /nix/store" on my BTRFS root with compress-force=zstd:6 Processed 974464 files, 327323 regular extents (751261 refs), 598287 inline. Type Perc Disk Usage Uncompressed Referenced TOTAL 40% 11G 28G 60G none 100% 2.7G 2.7G 6.2G zstd 34% 8.9G 25G 54G Nix also supports automatic deduplication using hardlinks which I have enabled in this case.