> I assume it's because the actual read-write head itself must among the most expensive parts to manufacture, Ehh a modern HDD is a marvel of precision manufac

> I assume it's because the actual read-write head itself must among the most expensive parts to manufacture, Ehh a modern HDD is a marvel of precision manufacturing and engineering. > rather than a bar fixed in place that spans entire radius of the writable surface, with an addressable strip of r/w heads that runs the length of it. Your bigger challenge is getting a set of read/write heads that are across the platter able to maintain a consistent height/etc. The closest I'm aware of, are the Connor 'Chinook' drives [0] that had two actuators, one on each side of the drive. Broadly speaking, I'd ask if multiple heads too close throw off decades of head design experience... [0] - https://en.wikipedia.org/wiki/Conner_Peripherals#/media/File:Conner_Peripherals_%22Chinook%22_dual-actuator_drive.jpg https://en.wikipedia.org/wiki/Conner_Peripherals#/media/File...