What you're describing is essentially how hybrid drives like the Momentus XT, as well as Apple's "Fusion Drive" software solution already work -- writes go to the HDD and are then pulled into the SSD for fast reads.
Also, I believe you could also achieve this at a software level with ZFS, which I understand allows you to do things like allocate an entire SSD (or multiple SSDs) as caches for other (presumably slower) drives.
writes go to the HDD and are then pulled into the SSD for fast reads.
With journalling?
Also, I believe you could also achieve this at a software level with ZFS, which I understand allows you to do things like allocate an entire SSD (or multiple SSDs) as caches for other (presumably slower) drives.
Careful reading, please. Journalling combined with the high throughput of spinning platters if you can create situations that eliminate seek and rotational latency is the key point here, not caching.
I guess I had trouble understanding your idea because it's contrary to one of the few principles in computer architecture that nobody has ever argued about.
You want to stick a spinning rust platter with moving parts in front of a solid-state memory that is several hundred percent faster for sequential tasks, and is an order of magnitude faster for random tasks?
Also, I believe you could also achieve this at a software level with ZFS, which I understand allows you to do things like allocate an entire SSD (or multiple SSDs) as caches for other (presumably slower) drives.