Adding SSD is not linear scaling. SSD has entirely different characteristics from rotational drives which in itself brings 1-3 orders of magnitude I/O performan

Adding SSD is not linear scaling. SSD has entirely different characteristics from rotational drives which in itself brings 1-3 orders of magnitude I/O performance improvement. Trying to fit high I/O workloads on spinning disks is a lot like spending your efforts to make your program run on 64K RAM. An interesting challenge, that would surely exercise your coding skills, but would not deliver the optimal performance.