The higher a disk's RPM, the faster its working speed. On the flip side, they offer the most significant memory sizes, and are cheaper than the other two memory options. Mac hard drives typically spin at rates of 5,400 to 7,200 RPM. They are also the most mechanized, with several moving parts. Of the three Mac memory types, traditional hard disks run on the oldest memory technologies. Traditional Hard Disks for More External Storage for Mac Sometimes, it may be necessary to use different hard disk types in your Mac, especially when you need both speed and capacity but your budget is limited. Traditional hard disks are bigger and cheaper. Mac hard drives are available in three primary forms: solid-state drives (SSDs), flash memory and traditional hard disks. SSDs are high-speed, and that makes them the go-to memory option for ardent gamers, graphic designers, and other professionals who value speed over all else.