[poser-boy]

I'd recommend checking out zpaq[1], it purposed for backups, and has great compression (even on low setting) for large 100GB+ file collections. However for smaller stuff I use zstd at level 22 in a tar for most things since it's much faster, though a little heavier.

[1] http://mattmahoney.net/dc/zpaq.html

[Klasiaster]

ZPAQ is the name of the tool but ZPAQ is also the name of the container format that gets used. ZPAQ embeds the decompression algorithm in the archive. One could store zstd-compressed blocks in ZPAQ archives as soon as a zpaql decompressor exists (e.g., for brotli there is a slow one implemented in a python subset and compiled to zpaql https://github.com/pothos/zpaqlpy).

I don't know exactly whether other formats are better for seeking and streaming, but since the baseline is tar, ZPAQ (in the 2.0 spec) is already better as it supports deduplication and files can even be updated append-only, and the compression is not an afterthought wrapped around it but well integrated.