DragonFly kernel List (threaded) for 2011-07
Re: Blogbench RAID benchmarks
:The results were taken for one run only, they were not averaged.
:Howewer, I repeated many times the tests for the RAID10 and RAID0 cases, and
:the numbers were always consistent (7% variation at worst).
:No fancy disk scheduler was used. Besides newfs, defaults were used for
Also, what blogbench command were you running? To get real results with
blogbench you have to remember that blogbench creates an ever-growing
data set and if the run isn't long enough the data set may not blow out
the buffer cache in one test, and blow it out in another, producing
radically different results.
I usually set --iterations=100 to force the blogbench data set to be
large enough to actually blow out the buffer cache.
You should include the raw blogbench output as well. It's a wall of text
but it is important because read activity can be very deceptive if a
filesystem bogs down on writes (because only writes expand the size of
the data set being read). This makes the final numbers a bit problematic,
requiring additional analysis to really understand what is going on.