I've made that point before on YC.[1] We need to view fast storage as something other than a disk accessed through the OS, and other than slow RAM accessed as raw memory. Access through the OS is too slow, and access as raw memory is too risky. What's probably needed is something like a GPU sitting between the CPU and the fast persistent storage. Call this an SPU, or "storage processing unit."
What would such a device do? Manage indices, do data transformations, and protect data. Database-type indices would be maintained by the SPU, so applications couldn't mess up the database structure. The SPU would manage locking, so that many non-conflicting requests could be serviced simultaneously. The SPU would have tools for doing searches. Regular expression hardware (this exists) would be useful. Record protection management (app can read/write part but not all of a record) would allow implementation of database type data access rules. Encryption and compression might be provided in the SPU.
There have been smart disk controllers before, but they haven't been that useful, since they couldn't make the disk go any faster. Now, it's time to look at that layer again. Some of the technology can be borrowed from GPUs, but existing GPU architecture isn't quite right for the job. An SPU will be doing many unrelated tasks simultaneously. GPUs usually aren't used that way.
[1] https://news.ycombinator.com/item?id=9964319