I would like to see a hybrid drive system where writes are first made to a journal which exists on a spinning platter, maintained in such a way that seek times are absolutely minimized. Then, the data is transferred to the flash side of the house.
This would result in a drive with fantastic throughput, except when immediately reading what was written. So long as there was a delay between writes and reads of the same data, it would look like a perfectly performing SSD. This could have fantastic properties for web applications. Given network latencies, many web applications could have considerable delays between the time data is written to disk and subsequently read.
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?
This would result in a drive with fantastic throughput, except when immediately reading what was written. So long as there was a delay between writes and reads of the same data, it would look like a perfectly performing SSD. This could have fantastic properties for web applications. Given network latencies, many web applications could have considerable delays between the time data is written to disk and subsequently read.