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I was just reading a presentation on SSD performance for PostgreSQL and came across a graph that made my head spin

If you eyeball it, it appears that the hard disk drive (HDD) is roughly 40% as fast as the solid state disk (SSD) for a specific test.  The presentation author did include the yellow star to the right highlighting the fact that the difference is actually 0.5%, but why not make the graph start at 0 so the graph visusally represented the results or  if the difference is that small, don’t have a graph at all and just say there is essentially no difference for this type of benchmark.

I think the way the graph was made was very likely the result of the default settings that the charting tool used, and I don’t think the author had any intention of misleading people (especially since he highlighted the real difference outside the graph),  but if I generated a graph that I felt didn’t reflect what I was trying to convey I would fix it or leave it out.

Besides the egregious graph, I think the presentation overall was very good.  I especially liked the recommendation section at the end, which was very actionable.

This entry was posted on Monday, April 6th, 2009 at 1:38 pm and is filed under presentations, technology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.