The Crucial MX300 750GB SSD Review: Micron's 3D NAND Arrives

Conclusions

It appears that the Crucial MX300 will be priced as a mid-range SATA drive or slightly below that. On a 'Price per GB' metric alone the 3D TLC NAND isn't starting any revolutions, which means that again the association between TLC NAND and lower performance still rings true. Despite this, the performance is clearly higher and above the current glut of planar TLC drives that are competing in a race to the bottom. 

One of the issues that Crucial will face is that despite being plus-one generation above the MX200, The MX300 is slightly slower and only by a small amount. It frequently straddles the dividing line between MLC performance and planar TLC performance. One issue on performance will be that it is also surpassed on several benchmarks by SanDisk's X400, one of the fastest planar TLC drives and a drive that will likely beat the MX300 on price. The 850 EVO level of performance is simply out of reach; Micron's 3D TLC drive is slower than Samsung's 3D TLC drive, and so will have to compete on price.

One thing to point out is that through our testing, we see that the MX300 has an acute weakness in its random read latency. At all but the highest queue depths it is half as fast as the top MLC drives that are only moderately faster than the MX200. Since this pattern holds at the lowest queue depths where parallelism and caching don't apply, there's a danger that this means Micron's 3D TLC is inherently quite slow to read from. This is most likely a carry on from when Micron implemented SLC write caching for the Crucial MX200:

With the MX200, the short-term performance boost of the SLC wasn't always worth the eventual cost of moving data from SLC to MLC. The SLC caching on the MX300 seems to greatly lower the power requirements of handling a small volume of writes, which may be a reason to use it even with the 3D MLC, especially if performance is sufficient to handle flushing a full write cache under load without a drastic slowdown. However, when the MX300's SLC write caching and spare area are exhausted, it slows down to the level of budget planar TLC drives. This is a drive that should not be filled to the brim and should not be subjected to enterprise workloads with heavy sustained writes.

Crucial SSDs: MX, BX and The Future

The future of Micron's Crucial SSDs is uncertain. When the MX100 launched, it was a hit by offering mainstream performance at great prices for the time. The BX100 showed up at even lower prices and with performance that was pretty close to the MX100. The MX200 added just enough performance to somewhat justify keeping two models around. Later the BX200 adopted TLC and sacrificed a lot of performance to cut costs, but failed to compete against the wave of budget drives based on Toshiba and Hynix TLC. Now that the MX line has also adopted TLC, it seems likely that the BX line will be retired along with planar NAND.

The interesting question is whether Crucial will introduce a higher end 3D MLC drive. We learned at Computex that a 3D MLC NVMe SSD will be released under Micron's Ballistix brand, a now separate sub-brand of Micron and different to Crucial. Thus the only potential for a new MLC drive from Crucial would be a high-end SATA drive. Many companies have been wondering whether it is worth trying to compete directly against the 850 Pro that has reigned for two years as the fastest SATA SSD and is very nearly the fastest possible SATA SSD (barring the use of pure SLC or 3D XPoint, neither of which will happen). Crucial might have the opportunity with Micron's 3D MLC to introduce a drive that is just as fast as the 850 Pro while being more power efficient, but it would still be tough to dethrone the 850 Pro unless Micron could also clearly undercut Samsung on price. Alternatively, we may see MLC become something that is mostly used on PCIe SSDs while the SATA SSD market is overrun by TLC.

Final Words

To put this into perspective, under ordinary consumer and end-user/home workloads, the MX300 performs at its peak near the top of the TLC charts. On most tests we found the MX300 to be remarkably power efficient. Other things being equal, TLC is typically slower and more power hungry than MLC, but the MX300 is more power efficient on most benchmarks than most MLC drives. Having this level of efficiency is extremely promising for Micron's 3D MLC and an accomplishment worth some kudos.