Compressed segments

It would be interesting to see the effect of compressing the segments within the tar files with a sufficiently effective and performant compression algorithm:

• Can we increase overall throughput by trading CPU for IO?
• Can we scale to bigger repositories (in number of nodes) by squeezing in more segments per MB and thus pushing out onset of thrashing?
• What would be a good compression algorithm/library?
• Can/should we make this optional?
• Migration and compatibility issues?