A recently released Intelligent I/O (I2O) subsystem for BSD type operating systems allows for very large I/O subsystems (up to 1600 drives per system), very fast I/O subsystems (in excess of 150 MB/Sec random I/O per controller, making it the FASTEST RAID subsystem for the PCI bus, regardless of O/S.). The I2o OSM (Operating System Module) is a highly scalable, runtime tunable I/O subsystem that allows easy and efficient tuning for various I/O loads. A study of this I/O subsystem demonstrates how a PC class server, with off the shelf hardware can be optimally adopted to mission critical I/O subsystems using open source software. Excellent I/O response with load averages in excess of 200.00 can be easily obtained.