Just keep a note about the performance comparison of bzip2 v.s. pbzip2. (Not professional and accurate...)
bzip2 is a freely available, patent free (see below), high-quality data compressor.
pbzip2 is a parallel implementation of the bzip2 block-sorting file compressor that uses pthreads and achieves near-linear speedup on SMP machines.
Here are the experiment results:
|pbzip2 with 2 processors||126.4s||
|pbzip2 with 4 processors||66.5s||
|pbzip2 with 8 processors||53.9s||
It's interesting that using 8 processors cannot double the compression speed of using 4 processors.
The test machine is 8cores Intel(R) Xeon(R) CPU E5620 @ 2.40GHz with CentOS 5.5.
The file to be compressed is a svn repository dump text file with size ~1.15GB:
pbzip2 with 2 processors
pbzip2 with 4 processors