Yeah i did some work to make sure that LoadError's thrown by require sigar don't hose the entire run.  In some cases there are collect_data(:default) blocks that do an explicit rescue of the LoadError and then have different non-sigar fallback code.  In other cases it just blows up because that's the only default behavior we have and you don't get your attributes in the default case without sigar installed.  collect_data(:sigar) was actually not doing anything, though and would never be run other than accidentally if it was paired up with a :default or :hpux or :aix that was getting run...