The Corsair MP400 is the company's first QLC-based solid-state-drive. It was released last year, but I haven't had the time to get the review finished until now. I was also waiting for feedback from Corsair regarding the strange write speed patterns in our thermal stress test, more on that later.

Corsair built the MP400 by pairing 96-layer QLC flash from Intel/Micron with the Phison E12S controller—a combination we've seen on the Sabrent Rocket Q before. Actually, both drives use the same Phison reference PCB design—the biggest difference seems to be that the Corsair MP400 in this review is 2 TB, and there is of course firmware secret sauce. Averaged over our real-life testing suite, the Corsair MP400 delivers very decent performance that's comparable to most entry-level TLC SSDs, like the ADATA Falcon, Swordfish, and HP EX900 Pro. Another important data point is that the highly popular Samsung 970 EVO is only 1% faster, the fastest PCIe Gen 3 SSDs are up to 9% faster, and the difference reaches 14% with PCIe Gen 4. Compared to SATA SSDs, the performance uplift is around 15%, 40% if you compare against QLC SATA—definitely something you'll notice in everyday usage.

Synthetic numbers of the Corsair MP400 confirm our findings, the drive's strongest suit is its high write performance, both in sequential and random IO, which is the backbone for the good real-life performance results. QLC flash improves the capacity by storing four bits of data per flash cell instead of three like TLC and two like MLC. While that obviously brings with it cost savings, the drawback is that writing to QLC is much slower than writing to TLC or MLC. In order to hide this performance penalty, all QLC-based SSDs operate some of their capacity in SLC mode, which is extremely fast to write to, but uses four times as much space. On the MP400, Corsair has configured the drive to use all capacity in SLC mode first, up to 500 GB—a quarter of the 2000 TB QLC capacity, and only then will the drive start flushing SLC to QLC with a significant performance loss—like all QLC SSDs. In our testing, we could write to SLC at 3 GB/s, but writing to QLC operated at only 250 MB/s. This is not as big a deal as it sounds right now and doesn't mean that once you're 25% full, you're only getting 250 MB/s writes. Our real-life testing happens with the SSD at 80% full, and we still got very decent performance out of the MP400.

Our thermal testing yielded interesting results for the MP400. While we couldn't get the drive to thermally throttle, we still saw interesting write speed patterns. These are not due to thermals because they are visible at much lower temperatures too, in our control test with a fan blowing onto the SSD. I suspect these are an artifact of how our thermal test stresses the flash/controller. I reached out to Corsair, and while there has been some back and forth, they haven't provided any useful explanation. I'll update this review if there are any new developments. It's more of a technical curiosity, not an actual issue—our real-life testing would have uncovered it otherwise.

With a retail price of $230, the MP400 is a little bit on the expensive side. While competing 2 TB QLC drives are similarly priced, I feel like that isn't enough to make me overlook the various QLC drawbacks compared to TLC. 2 TB TLC alternatives worth considering are the Team Group Cardea Zero for $205, ADATA Swordfish for $210, ADATA SX8200 Pro for $240, and HP EX950 for $250. Strong competition also comes from the Crucial P1, which is currently $225, but can be found at quite a discount fairly often. Don't get me wrong, the MP400 is a very capable SSD that's great for light consumer workloads and a huge upgrade over any HDD-based setup, but the pricing is just a little bit high. If Corsair can bring its price down to around $200, possibly below, it would suddenly become a tempting alternative to many 1 TB SSDs—spend just ~$50 to double your capacity with only a marginal performance hit in most workloads. Power users who write dozens of GB every single day should be looking at TLC SSDs though, possibly PCIe Gen 4, at much higher pricing, of course.