SSDs are fine for a computer with a single drive that everything. My personal opinion, based on testing using virtually unlimited number of SSDs, is that for the most part putting your operating system and applications on an SSD is a total waste of money. Yeah, it boots faster. But I am not one to boot a computer very often. And once booted, the OS and applications are in memory and the SSD doesn't really do much if anything for performance.
Depending on what you use your computer for, storing the data on SSDs would make a big improvement in performance. That is if you can afford to get enough SSD capacity to handle the needs.
We absolutely can build a RAID using regular old spinning disks that is every bit as fast as SSDs for move large quantities of data. The key here is that RAIDs do big file transfers better than anything. Itsy bitsy little transfers are best on SSDs. But for a big database nothing beats a big RAID with spinning drives.
Rick
molṑn labe'
"I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin