Do you know about OS-level I/O caching/buffering? They make the sequential speed more important. And in case one wants to get faster, there is no need to go all

Do you know about OS-level I/O caching/buffering? They make the sequential speed more important. And in case one wants to get faster, there is no need to go all SSD. There is often a lot of data but I/O touches only small part of it, so one can use few fast cache SSDs + many spinning disks in a cluster to achieve good enough performance with better price. There you go, spinning drives still make a lot of sense.