Results: 128 KB Sequential Write
128 KB Sequential Write
Unlike sequential reads, sequential writes tend not to scale according to queue depth. Writes are actually more dependent on the number of dies a given task can be spread across. For example, higher density means that the 120 GB M500 sports just eight dies, whereas the 128 GB m4 had 16. That explains why the two lower-capacity M500s trail the previous generation at their respective capacities.
We have a hard time making a big issue out of this, particularly when the larger models are so much quicker than their predecessors. The quickest m4 topped out near the 265 MB/s mark, while the larger M500s exceed 400 MB/s. The difference isn't earth-shattering, but it's difficult to imagine a desktop application where higher sequential writes might change the experience drastically.
We add in data from elsewhere in the consumer SSD space, and Crucial's larger M500s are up there in the action. It'd be an exaggeration to say that the Extreme II, 840 Pro, and OCZ Vector pistol-whip the 480 and 960 GB Crucial drives. However, a 100 MB/s lead in favor of OCZ's Vector does seem a little brutal. Now's probably a good time to mention that there are SSDs framed as mainstream and others marketed as performance-oriented. The M500 falls into the former category, while the Vector, 840 Pro, and Extreme II are categorically high-end drives where speed is concerned.
If we chart out the maximum observed 128 KB sequential write performance from Iometer, it becomes apparent that the 120 GB M500 is not stellar when it comes to writes. Neither is Samsung's 120 GB 840. Achieving half (or less) of the performance posted by two-bit-per-cell-based SSDs sporting similar capacity, the Crucial and Samsung models are particularly hobbled. One is hamstrung by TLC NAND, while the M500 is hurt by a move to higher-density 128 Gb flash.
The M500 and 840 butt heads again at 240 GB, where Crucial's margin of victory is just 8 MB/s. Samsung's 840 EVO is another matter entirely. Once its Turbo Write buffer runs out, though, it's back down to the regular 840's performance level.