How about making RAID internally on hard drive platters

[prehensile]

Seeing as there is already dual channel ram and raid arrays to make data transfer faster, shouldn't it be possible to make dual channel platters or a raid array covering 2/6 platters to have hard disks going six times as fast?

[arthurleung]

Bits in a harddrive does not align well. Unlike dual channel ram, the ram address is fixed.
On different harddrives in RAID arrays, the address is the same, the position does not matter since the controller take care of it.

Using dual channel platters you need 2 perfectly identical platters which is impossible to make. (Even if you can make, the physical platter will More likely become less aligned over time.) If you opts for multiple heads and arms, they may interfere with each other's magnetic field and decrease writing accuracy, more errors, etc.

It is just easier, cheaper and more reliable to have 1 thread going on the same time only. Your suggestion will only help STR but not seek time. There are multiple heads in a harddrive but only one is working at any given time.

[HKPolice]

If the heads are able to move independantly, this would work. But that's too hard to engineer right now I assume. You'll basically need 1 HD controller for each platter.