If you are interested in a deeper look at the SanDisk Extreme II architecture we're already published an Architecture Deep Dive earlier today. This review will touch on some of the facts in that article, but we're going to expand on the NAND flash a bit more here.
Nearly a year ago we sat down with two SSD's at Computex for an early look at IMFT 20nm flash and Toshiba 19nm Toggle Flash. Both drives used identical LSI SandForce SF-2281 controllers and matching firmware. By the time we walked away, it was clear that 20nm ONFi flash had lost a lot of performance compared to 25nm ONFi, and that 19nm Toggle wasn't much different than 24nm Toggle when it came to performance. At the time we thought IMFT would get it together, but now that we have real products in hand, it's becoming clear that 20nm ONFi flash isn't very good for smaller capacity SSD's, like the 120GB capacity size.
Even though today's review is on the SanDisk Extreme II, I can't help myself from drawing attention to the 19nm vs. 20nm differences. The SanDisk Extreme II uses the Marvell 88SS9187 controller, the same as the Plextor M5 Pro / Xtreme and Crucial M500. Since we have all of these drives in the 128GB class size, we can see how NAND flash affects performance. A large portion of our Architecture Deep Dive linked above talks about SanDisk's new ALB flash with nCache.
Marvell doesn't deliver programming / firmware with their products so if you want to use a Marvell SSD controller, you need to build your own firmware, like SanDisk did. The other option is to go to a third party like LiteOn or MemoRight to have it made for you. When you use a third-party firmware, you need to work with them on fixing issues that may pop up. Working with a third-party means delays, something SanDisk wants to avoid after the original Extreme SSD issues.