Not that many 18TB SSDs available though. Might (and probably will) change in the future, but today, if you want massive amounts of storage, HDDs are your only reasonable solution unless you really require the read & write speeds of an SSD.
Imagine Backblaze trying to replace their 46000 16TB HDDs with a few hundred thousand smaller SSDs in their datacenter.
Not that many 18TB SSDs available though. Might (and probably will) change in the future, but today, if you want massive amounts of storage, HDDs are your only reasonable solution unless you really require the read & write speeds of an SSD. Imagine Backblaze trying to replace their 46000 16TB HDDs with a few hundred thousand smaller SSDs in their datacenter.