Dual actuators don't actually double IOPS/TB for all sorts of reasons - queuing effects, contention for resources elsewhere in the drive, or limitations of the

Dual actuators don't actually double IOPS/TB for all sorts of reasons - queuing effects, contention for resources elsewhere in the drive, or limitations of the external interface. In practice it tends to be far short of double, so you're better off planning for larger numbers of (possibly smaller) drives with the same capacity and IOPS than for single drives getting faster by any measure.