Samsung 860 QVO (1TB, 4TB) SSD Review: The First QLC SATA Consumer

The introduction of four-bit NAND flash memory per cell (QLC) continues with Samsung launching their first consumer SATA SSD with QLC NAND. The new 860 QVO sets a new entry-level standard in Samsung's highly successful SSD range. Unlike previous low-end offerings like the 750 EVO and the 850 plain, the 860 QVO gets a wide output and is here to stay.

Samsung 860 QVO: Koo-vo?

The Samsung 860 QVO is the first of a new wave of SATA SSDs that should be able to beat prices on SSDs even without DRAM TLC thanks to the increased density of the QLC NLC – and the 860 QVO itself is equipped with Cache LPDDR4 DRAM.

Samsung's SATA consumer product line now includes the 860 QVO, 860 EVO and 860 PRO models. The 860 QVO, EVO, and PRO models share a common hardware platform based on Samsung's MJX SSD controller and their 64-layer NAND 3D, with product levels varying primarily by the number of bits stored per flash memory cell.

The 860 QVO, provided in the box, is rated at a write endurance rating of 0.3 DWPD (Drive Writes Per Day), which, even for 1 TB, equals 300 GB per day, which exceeds most user workloads. The price is set at $ 150 for the smallest 1 TB model, up to $ 600 for the 4 TB model, which equates to an equivalent cost per GB for the entire range. It should be noted that The MSRP for introducing the 860 QVO is not as aggressive as the record sales we've seen recently on TLC SSDs.

MLC vs. TLC vs. QLC: Why QLC is important

The two-bit MLCs used in the 860 PRO are now quite rare in the consumer SSD market and almost completely absent from today's enterprise SSDs, having been largely replaced by a three-bit-per-cell MCC such as used in the 860 EVO. With every increase of bits stored per cell, performance and write endurance decrease because SSDs need to be more careful to distinguish between voltage levels, which can reach 16 for NAND QLC.

While controller advancements and other improvements to the NAND process (including moving from the NAND plane to the NAND 3D) have allowed TLC to overcome almost all of its disadvantages compared to the MLC, the QLC NLC should not be doing so. much. Early projections for QLC NLC required up to a few hundred cycles of programming / erasure, which would produce disks requiring careful processing with a workload that more or less treats storage as a WORM media (write-once, read-many ). As QLC moved closer to mbad production, the story changed and it became clear that the QLC NLC would have enough endurance to be used as a versatile storage.

Intel and Micron were the first to send their NAND QLC, initially in the company SATA SSD Micron 5210 ION, and then in the M.2 NVMe mainstream SSD Intel 660p and Crucial P1. The 660p and P1 have introduced QLC NAND into the mainstream SSD market, but as NVMe drives, they are still priced higher than SATA SSDs. However, as mentioned above, the introductory PRMs for the 860 QVO are not aggressive at all compared to the record sales we've seen on TLC SSD drives recently. These sales are not entirely due to the holiday season: prices of flash memory have generally dropped, now that everyone has his NAND 64 layers in mbad production while sales of PCs and smartphones have slowed. Rumors indicate that yields on QLC NLCs have been low, so the actual cost is close to that of TLC instead of reflecting the ideal reduction of 25% per GB.

The two main weaknesses of the QLC NLC over the more traditional NAND TLC NAND are write performance and write endurance. Both problems can be mitigated by the use of a larger total number of NANDs, which makes it possible to spread the writes over more NAND matrices in parallel. This and the (hopes of) lower prices make the QLC NAND the most suitable for high capacity SSDs. Thus, the 860 QVO product line starts at 1 TB. Even at this capacity, the 860 QVO only needs 8 NAND QLC arrays and can not maintain 80 MB / s writes. This means that the SLC write cache on the QVO 860 is even more important than for TLC SSDs. When working in the cache, the 860 QVO can saturate the SATA link with random or sequential writes. The cache operates in the same way as the SLC cache on the 860 EVO, with a capacity of at least 6 GB when the drive is relatively full at 42 GB for the 1 TB model or 78 GB for the 2 TB and 4 TB models. . The Intel and Crucial QLC consumer discs also have SLC caches of varying size, but with much higher limits on the maximum size of the cache and a cache retention policy until the drive has need more space. In contrast, the 860 QVO appears to be adopting a more traditional approach of aggressively clearing the cache during periods of inactivity in order to prepare for future writing activities.

The performance specified for the QVO 860 when running out of the SLC cache is typical for a consumer SATA SSD. Once the cache is filled, the performance drops significantly, the sequential writes indicating the most serious effect. Power consumption is also comparable to Samsung's other recent SATA SSDs, with the 1TB model requiring just over 2W at the tip, and larger models up to 3W in writing. The performance of the 2TB and 4TB models is almost identical, indicating that 2TB of QLC is sufficient to fill all the NAND channels of the MJX controller.

The 860 QVO guarantee and endurance indices are the other free domain in which the use of QLC NAND has repercussions. The warranty period of the 860 QVO is three years. It is typical of low-end SSDs, but is less than 5 years of 860 EVO and PRO systems. The write endurance is evaluated for 360 full reader writes or 0.3 DWPD for the duration of the 3 year warranty. This is comparable to some of the cheaper TLC drives currently on the market, and in terms of the total number of bytes written, the 860 QVO rating is about 80% higher than that of the Intel 660p and Crucial P1 processors, though that these NVMe QLC disks have the advantage of five. -Year of warranty.

The 860 QVO's case uses the same basic design as Samsung's other recent SATA SSDs, but is painted in dark gray instead of Samsung's traditional black. Internally, the QVO 1TB 860 illustrates the comic way to oversize, even the 2.5-inch drive form factor, compared to the requirements of modern consumer SSDs. An empty block on the back can hold another NAND package. Samsung packs up to sixteen NAND arrays together, so even the 4 TB QVO can cope with this same small circuit board: the most important problem is place a DRAM memory. Samsung states that its current MJX controller supports up to 8TB of SSDs, but it is clear that the demand for consumer SSDs is still very low. The 2.5 "form factor itself can now accommodate at least 16TB, or 32TB if two circuit boards are stacked in a 15mm thick drive format.These capabilities can appear in business products but it will probably take several generations before they reach the mainstream SSD market.

Samsung has not announced M.2 version of the 860 QVO, but this is clearly possible if the demand exists. They can probably fit even the 4TB 860 QVO on a single-sided 80 mm M.2 card.

Launch PSMs for the 860 QVO do not compare favorably with SATA SSDs already on the market. The 860 EVO is currently below the threshold of 15 cents per GB for 1TB and 2TB, and many other consumer TLC drives are priced at similar prices. Samsung currently has no competition in the 4TB SATA SSD space. As a result, their 4TB 860 EVO is significantly more expensive per GB, leaving a sufficient margin below the 860 QVO. To be a powerful competitor in the consumer market, the 860 QVO must actually cost only 13 cents per GB. This limit may fall further in the coming months, as flash memory prices continue to fall and yields QLC improve.

A note on our tests: the occasional failure of the reader

Samsung has provided us with 1 TB and 4 TB 860 QVO samples. The tests of the 1 TB model went well, but the 4 TB 860 QVO encountered some problems, causing the drive to disappear from the system interface. These issues are especially noticeable when hot-swapping the drive, which is part of our SATA SSD test routine. It has also been difficult to recognize the 4TB drive by a motherboard during the boot process, which has the effect of blocking the boot indefinitely on some of our systems.

It should be noted that our test regime is quite strict and that we sometimes encounter disk failures. This happens and only a few are specific to a reader.

Therefore, these issues do not appear to be specific to the QVO 860 or its use of the QLC NAND and have been replicated to both the 4TB 860 EVO and the 4TB 860 PRO with multiple host systems, but have not occurred with any of the systems. smaller ones. 860S. The 3.84 TB 860 DCT and the 4TB 850 EVO also ran smoothly. This is not a problem for 4TB SSDs in general. We are still working with Samsung to determine the extent and nature of these problems with 4TB disks, and it is not yet clear whether there is a general compatibility issue or whether our procedure is test has caused a firmware bug that places our samples permanently in a file. uncooperative mood.

Because of these issues, some benchmark results for 4TB disks have been delayed. Notwithstanding performance and price, I can not recommend any of the 860 series 4TB SSDs without a better understanding of the nature of the issues.

The competition

There are still no other mainstream QLC SATA SSDs on the market, although ADATA has announced the SU630, which will offer extremely low capacity. The Intel 660p and Crucial P1 processors are the only other consumer-grade QLC SSDs currently available, but their price is tailored to the NVMe market. The majority of the competition for the 860 QVO will come from SSD SATA drives with TLC NAND, entry-level models with DRAM-free controllers (eg, Toshiba TR200) ​​and more traditional models like the 860 EVO , Crucial MX500 and WD Blue. Almost all SATA SSD product lines feature a 1TB clbad, but there are still relatively few 2TB models and no 4TB competitor has been announced. This will probably change as more QLC drives come on the market and even 2 TB TLC drives are becoming more common this year.