Hitachi today is now shipping one-inch diameter drives storing 4 gigabytes with a a data transfer rate that is 70 percent faster than the previous-generation Microdrive. Hitachi reckons it’s the “world’s smallest hard disk drive“, weighing just over a half an ounce and equivalent in size to a matchbook.Hitachi will continue to offer its current 1GB Microdrive to customers throughout the world and is planning to introduce a 2GB version of the Microdrive later this year. The company expects the new 4GB Microdrive 3K4 to be available on retail shelves in major markets this November for about $500.