> in the case of the HS760, WD adds a second actuator to the drive, essentially splitting it up into two quasi-independent drives with each half having domain o

> in the case of the HS760, WD adds a second actuator to the drive, essentially splitting it up into two quasi-independent drives with each half having domain over 4.5 platters (9 surfaces) To me it would make more sense to divide the drive up by cylinders instead of platters, ie, the first actuator has access to cylinders 0 to N/2 and the 2nd accesses cylinders N/2+1 to N. This would give you roughly the same sequential performance but decrease average seek performance for random seeks.