Hard drives are much higher density already. A quick search shows estimates of 1-2 Tbit/square inch for recent techniques like SMR or HAMR. Remember that a tap

Hard drives are much higher density already. A quick search shows estimates of 1-2 Tbit/square inch for recent techniques like SMR or HAMR. Remember that a tape has a huge amount of surface area compared to the small track area of a few discs. The material science aspects of that flexible tape flying by a helical scanning head are quite different from the circular tracks of a hard disk.