Intelligent Input/Output (I2O) is a hardware specification that describes a model for offloading I/O processing from the CPU. There is no doubt that this is leading to extremely high performance I/O.

I20 definition by Brent Sullivan.

High-performance servers will start using a new I/O architecture to boost performance without costing a fortune. From '97, written by Tom Thompson.

From Webopedia, definition of I2O and links.