I'm not the only one to have noticed this, but I spent a
sufficient amount of time banging my head against a
wall finding this out that I thought it important to make more
people aware of this.
While trying to validate new database hardware we were seeing some serious performance issues in production. Most MySQL benchmarks using sysbench or pt-playback couldn't reproduce it, but a simple sysbench 16 threaded filio test on the mysql partition showed about 1/3 the throughput we would expect. The fact that much of the hardware was new as well as the OS we were using made tracking down the cause difficult (changing …