I'm also curious about the choice of LZ4. It's fast, but its compression is pretty awful. For example, on simple, regular text (JSON) files I'm seeing about 45

I'm also curious about the choice of LZ4. It's fast, but its compression is pretty awful. For example, on simple, regular text (JSON) files I'm seeing about 45% worse compression than plain gzip (default compression level). I hope at least it's using the highest compression level, but I've found that "lz4 -9" is about as slow as "gzip -6", still with worse compression. I'd be happier if the choice of compression was dependent on the size of files. The larger a file, the more you gain from compression. Does Arq skip compression for already-compressed files (.gz, .xz, .bz2 etc.)?