There are still a lot of workloads that perform mostly sequential writes and reads that aren't a huge win for SSD. Even if you look at random write workloads ma

There are still a lot of workloads that perform mostly sequential writes and reads that aren't a huge win for SSD. Even if you look at random write workloads many of those start by journaling to a WAL now, so it is possible for the WAL to be on a separate HDD. I assume a lot of this comes down to "object storage": S3 and similar services. As I understand it, these would do actual data storage in HDD (or other cheaper medium for glacier and slower access storage). Metadata caching could use SSD.