Results: Sequential Performance
Fantastic sequential read and write performance is a trademark of modern SSDs. To measure it, we use incompressible data over a 16 GB LBA space, and then test at queue depths from one to 16. We're reporting these numbers in binary (where 1 KB equals 1024) instead of decimal numbers (where 1 KB is 1000 bytes). When necessary, we also limit the scale of the chart to enhance readability.
128 KB Sequential Read
Before we get too obscure with the benchmarks, I'll start with the basics. Sequential reads are somewhat mixed between these four reference-class drives equipped with different types of NAND. The SSD armed with Intel's L85C only picks up speed at the end, as queue depth increases. The L85A- and A19-based models get near or pass the 500 MB/s barrier.
Between 520 to 530 MB/s is the practical limit of SATA, and that's where the two ONFi-capable models peak (ONFi stands for Open NAND Flash Interface, by the way, which is a workgroup that created an interface standard for certain flash components). The drives sporting A19 NAND are a little different; they don't demonstrate as high of a read throughput ceiling, which is typically of the Toggle-mode DDR interface. But this will probably be the last time you see the ONFi flash win.
128 KB Sequential Write
Typically, when I test four drives, I get different capacities. Those capacities often behave differently on a benchmark chart due to their die and package configuration. In this case, however, there is significant differentiation from only two capacities. Why? The NAND interface types matter. A lot. The 256 GB model equipped with Toshiba's A19 flash takes top honors by achieving 450 MB/s, followed by the 128 GB drive sporting the same stuff.
Both ONFi-capable drives appear further down the list. Combining JMicron's controller and L85A flash results in just under 250 MB/s, while the 128 GB L85C-armed model falls 100 MB/s behind. Really, these numbers aren't surprising, given fewer die available for interleaving on the SSD with L85C NAND.
