Fast compression in 7z format (like zip or gzip)


In short: can the Deflate compression be used only with the zip format (-tzip) in 7zip?

I want to archive a big directory (hundreds GiB) from a disk to another, while keeping I/O speed the same or better than without compression.

I like the 7z format for a variety of reasons, but LZMA and Bzip2 compressions are too slow even with -mx=1. I've tried 7z a -mm=Zip -mx=1 -mmt=4 (and -mm=GZip which uses Deflate too), but I get an argument error after the file scanning phase.

My typical solution would be tar with .tar.lzo (LZOP), which easily reaches 100 MiB/s single-threaded at default compress rate; or .tar.gz with GZIP=-1. A very fast compressor is lbzip2 with multithreading, but it cannot be run from tar itself.

My source disks typically read at 20 MiB/s, sometimes 100 (with files several MiB big); the target writes at up to 80 MiB/s. So this is the speed the compressor should have, ideally even when single-threaded. Up to 8 cores and 16 GB RAM are available.

Best Answer

You could try the 7-Zip Zstandard version. This fork supports additional codecs which are very fast for compression and decompression.

Here is a short summary of the codecs used:

  1. LZ4 - fastest compression / decompression, but not much compression ratio

  2. Lizard / LZ5 - better ratio then LZ4 and often faster on decompression then LZ4... but compression is a bit slower

  3. Brotli and Zstandard - zstd is often a bit faster then Brotli, but for text content, Brotli maybe is a bit better ;)

Threading is supported by all 5 codecs, up to 256 threads currently.

Run it like:

7z a archiv.7z -m0=lz5 -mx1 -mmt=4

7z a archiv.7z -m0=zstd -mx1 -mmt=4

7z a archiv.7z -m0=brotli -mx1 -mmt=1 .. 7z a archiv.7z -m0=brotli -mx1 -mmt=256

And so on...