bzip2 has always been parallelizable. At one point a few years ago I was working on a compressed file format with that included compressed block metadata, beca

bzip2 has always been parallelizable. At one point a few years ago I was working on a compressed file format with that included compressed block metadata, because bzip2 is most efficient when it gets about ~900kB to compress at a time. In effect, you split the file up into 900kb chunks, compress them in parallel, and recombine them into one file at the end.