The newest and best MLC (Multi Level Cell) and TLC (Triple Level Cell) NAND technology both feature an emulated layer of SLC (Single Level Cell) baked right in. This emulated SLC layer is used to both accelerate write programming, and enhance endurance by consolidating random segments, and then flushes them sequentially to the larger MLC/TLC NAND array.
SLC emulation is accomplished by programming two or three bit per cell NAND Flash with one bit per cell. Programming a single bit per cell can be accomplished at a lower latency, which accelerates write speed. Programming a single bit per cell takes less voltage to perform, which translates into increased endurance. So, it's pretty easy to see why a pseudo layer of SLC will enhance the performance and longevity of MLC/TLC NAND Flash, and why we are seeing a trend towards this new technology.
Pseudo is nice, but it's nothing like the real deal. Originally, NAND Flash was all SLC, but the cost of production was, and still is, prohibitive to consumer SSD implementation. SuperSSpeed's S301 is a really rare bird. The S301 is a surprisingly affordable consumer based SSD, with a 100% SLC NAND Flash array onboard. No pseudo layer or fancy programming. It's the real deal.
There is a common misconception, perpetrated by the SSD industry, that an SSD's controller is primarily responsible for producing the speed of an SSD. Equally as important to performance is the quality, and type of NAND Flash utilized. One could even say that the NAND is actually more important than the controller when you consider that 85% of the cost of building an SSD is the NAND.
They say a picture is worth a thousand words, and I couldn't agree more:
The only real difference between these three SSD's is the NAND Flash. All three have the exact same LSI SandForce 2281 controller on board, as well as NAND arrays of identical capacity. Going left to right, we have MLC Asynchronous NAND, MLC Synchronous NAND, and finally (the good stuff), SLC Synchronous NAND.
As most of you know, capacity has a large impact on an SSD's write speed. Typically, the smaller the capacity, the slower the drive.
Today, we are going to show you what happens when you pair the highest quality NAND (SLC) with your average everyday SandForce 2281 SSD controller, and a very small capacity RAID 0 array. Let's see how this tiny array stacks up against the big boy's.