Earlier this week, Daniel Flores posted the first-week report on his Google Summer of Code project, file compression in Hammer.  He mentioned that the LZ4 algorithm he is using seems to have the best performance with repeating text data, as in logfiles.  I asked for numbers, and he provided them.  The important data in the results is the total compression column.  It shows how many 64k blocks were able to be compressed, with that type of data.