The introduction of four bit per cell (QLC) NAND flash memory continues with Samsung's launch of their first consumer SATA SSD with QLC NAND. The new 860 QVO establishes a new entry-level tier in Samsung's highly successful SSD product family. Unlike previous low-end offerings like the 750 EVO and the plain 850, the 860 QVO is getting a broad release 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 the prices on even DRAMless TLC-based SSDs thanks to the increased density of QLC NAND—and the 860 QVO itself is equipped with a full-size LPDDR4 DRAM cache.

Samsung 860 QVO Primary Specifications
Capacity		1 TB	2 TB	4 TB
Form Factor		2.5" 7mm SATA
Controller		Samsung MJX
NAND Flash		Samsung 1Tb 64L 3D QLC
DRAM (LPDDR4)		1 GB	2 GB	4 GB
Sequential Read		550 MB/s
Sequential Write	SLC Cache	520 MB/s
	QLC	80 MB/s	160 MB/s	160 MB/s
Warranty		3 years
Write Endurance		360 TB 0.3 DWPD	720 TB 0.3 DWPD	1440 TB 0.3 DWPD
MSRP		$149.99	$299.99	$599.99

Samsung's consumer SATA product line now consists of the 860 QVO, 860 EVO and 860 PRO. The 860 QVO, EVO and PRO all share a common hardware platform based around Samsung's MJX SSD controller and their 64-layer 3D NAND, with the product tiers differing primarily in the number of bits stored per flash memory cell.

The 860 QVO, from the box, is given a write endurace rating equivalent to 0.3 Drive Writes Per Day (DWPD), which even for the 1TB means 300GB a day, every day, which goes above and beyond most consumer workloads. Pricing is set to run at $150 for the smallest 1TB model, up to $600 for the 4TB model, making an equal cost per GB for the full range. It should be noted that the introductory MSRPs for the 860 QVO are not that aggressive in comparison to the record-setting sales we've been seeing on TLC SSDs recently.

MLC vs TLC vs QLC: Why QLC Matters

Two bit per cell MLC as used in the 860 PRO is now quite rare in the consumer SSD market and almost entirely absent from current enterprise SSD, having been largely replaced by three bit per cell TLC as used in the 860 EVO. With each increase in bits stored per cell, performance and write endurance decrease as SSDs need to be more careful to correctly discriminate between voltage levels, now up to 16 for QLC NAND.

While controller advances and other NAND process improvements (especially the switch from planar to 3D NAND) allowed TLC to overcome almost all of its disadvantages relative to MLC, QLC NAND is not expected to do the same. Early projections for QLC NAND called for at most a few hundred program/erase cycles, which would produce drives that would require careful treatment with workload that treated the storage more or less as a write-once, read-many (WORM) media. As QLC got closer to mass production, the story shifted and it became clear that QLC NAND would have adequate endurance for use as general-purpose storage.

Intel and Micron were the first to ship their QLC NAND, initially in the Micron 5210 ION enterprise SATA SSD and then in the Intel 660p and Crucial P1 consumer M.2 NVMe SSDs. The 660p and P1 introduced QLC NAND to the consumer SSD market, but as NVMe drives they still carry a price premium over SATA SSDs. However, as mentioned above, the introductory MSRPs for the 860 QVO are not at all aggressive in comparison to the record-setting sales we've been seeing on TLC SSDs recently. Those sales are not due entirely to the holiday season—flash memory prices in general have been crashing now that everyone has their 64-layer NAND in full mass production while PC and smartphone sales have been slowing. Meanwhile, rumors indicate that yields on QLC NAND have been poor, so the true cost is close to that of TLC instead of reflecting the ideal 25% discount per-GB.

Samsung 860 QVO Secondary Specifications
Capacity		1 TB	2 TB	4 TB
DRAM (LPDDR4)		1 GB	2 GB	4 GB
SLC Cache Size	Min	6 GB	6 GB	6 GB
	Max	42 GB	78 GB	78 GB
Sequential Read		550 MB/s
Sequential Write	SLC Cache	520 MB/s
	QLC	80 MB/s	160 MB/s	160 MB/s
Random Read IOPS	QD1	7.5k (SLC) 4.4k (QLC)
	QD32	96k (SLC) 36k (QLC)	97k (SLC) 60k (QLC)
Random Write IOPS	QD1	42k (SLC) 21k (QLC)	42k (SLC) 38k (QLC)
	QD32	89k (SLC) 21k (QLC)	89k (SLC) 40k (QLC)	89k (SLC) 42k (QLC)
Power	Read	2.1 W	2.3 W	2.3 W
	Write	2.2 W	3.1 W	3.1 W
	Idle	30 mW	30 mW	30 mW
	DevSlp	3 mW	3.5 mW	7 mW

The two main shortcomings of QLC NAND relative to the more mainstream TLC NAND are in write performance and write endurance. Both problems can be alleviated by the use of more NAND total, allowing writes to be spread across more NAND dies in parallel. That and the (hopes of) lower prices make QLC NAND best suited for large capacity SSDs. Thus, the 860 QVO product line starts at 1TB. Even at that capacity, the 860 QVO only needs 8 dies of QLC NAND and can only sustain writes at 80 MB/s. That means that the SLC write cache on the 860 QVO is even more important than for TLC SSDs. When working within the cache, the 860 QVO can saturate the SATA link with random or sequential writes. The cache functions much the same as the SLC cache on the 860 EVO, with a capacity that varies from a minimum of 6 GB when the drive is relatively full, up to 42 GB on the 1TB model or 78 GB on the 2TB and 4TB models. The Intel and Crucial consumer QLC drives also feature variable-size SLC caches but with much higher limits on the maximum cache size and a policy of retaining data in the cache until the drive needs the extra space. By contrast, the 860 QVO seems to take a more typical approach of aggressively flushing the cache during idle time in order to prepare for future bursts of write activity.

The performance specs for the 860 QVO when operating out of the SLC cache are typical for a mainstream SATA SSD. After the cache is full, performance drops significantly, with sequential writes showing the most severe effect. Power consumption is also comparable to Samsung's other recent SATA SSDs, with the 1TB model requiring a little over 2W at peak and the larger models drawing just over 3W during writes. The 2TB and 4TB models have very nearly identical performance and power ratings, indicating that 2TB of QLC is sufficient to populate all the NAND channels of the MJX controller.

The warranty and endurance ratings for the 860 QVO are the other clear area where the use of QLC NAND has its impact. The 860 QVO's warranty period is three years, typical for low-end SSDs but shorter than the 5 years that the 860 EVO and PRO carry. Write endurance is rated for 360 full drive 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 total bytes written the 860 QVO's rating is about 80% higher than the Intel 660p and Crucial P1, despite those NVMe QLC drives having the advantage of a five-year warranty.

The 860 QVO's case follows the same basic design as Samsung's other recent SATA SSDs, but is painted dark gray instead of Samsung's traditional black. Internally, the 1TB 860 QVO illustrates how comically oversized even the 2.5" drive form factor is compared to the requirements of modern consumer SSDs. The PCB features three main BGA packages: the DRAM, the controller, and the stack of eight 1TB QLC dies. There's an empty pad on the back that can accommodate another NAND package. Samsung commonly packages up to sixteen NAND dies together, so even the 4 TB QVO may be able to get by with this same small PCB—placing DRAM becomes the more important problem. Samsung states that their current MJX controller supports up to 8TB SSDs, but there's clearly very little demand for consumer SSDs in that capacity yet. The 2.5" form factor itself can now accommodate at least 16TB, or 32TB if two PCBs are stacked in a 15mm thick drive. These capacities may show up in enterprise products, but are probably still several generations away from hitting the consumer SSD market.

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

Samsung 860 Family Price Comparison
Capacity	NAND	250GB 256GB	500GB 512GB	1TB	2TB	4TB
860 QVO (MSRP)	QLC	N/A -	N/A -	$149.99 (15¢/GB)	$299.99 (15¢/GB)	$599.99 (15¢/GB)
860 EVO	TLC	$55.99 (22¢/GB)	$72.99 (15¢/GB)	$127.98 (13¢/GB)	$294.88 (15¢/GB)	$797.99 (20¢/GB)
860 PRO	MLC	$97.00 (38¢/GB)	$147.00 (29¢/GB)	$284.99 (28¢/GB)	$577.99 (28¢/GB)	$1179.99 (29¢/GB)

The launch MSRPs for the 860 QVO do not compare favorably against SATA SSDs already on the market. The 860 EVO is currently below the QVO's 15 cents per GB at 1TB and 2TB capacities, and plenty of other mainstream TLC drives are priced similarly. Samsung currently has no competition in the 4TB SATA SSD space, so their 4TB 860 EVO is substantially more expensive per GB, leaving appropriate room below for the 860 QVO. In order to be a strong competitor in the consumer market, the 860 QVO really needs to priced at no more than 13 cents per GB, and that limit is liable to come down further over the next several months as flash memory prices continue to drop and QLC yields improve.

A Note on Our Testing: The Occasional Drive Failure

Samsung provided us with samples of the 1TB and 4TB 860 QVO. Testing the 1TB model went smoothly, but the 4TB 860 QVO has run into some problems causing the drive to disappear from the system interface. These issues are most noticeable when hot-swapping the drive, which is a regular part of our SATA SSD testing routine. There have also been challenges getting the 4TB drive recognized by a motherboard during the boot process, and this causes the boot to stall indefinitely on some of our systems.

It should be noted that our testing regime is fairly streunous, and we sometimes get drive failures. It happens, and only a few of them are ever drive specific. 

As a result, these problems do not appear to be specific to the 860 QVO or its use of QLC NAND and have been replicated on both the 4TB 860 EVO and 4TB 860 PRO with multiple host systems, but have not occurred with any of the smaller 860s. The 3.84 TB 860 DCT and the 4TB 850 EVO have also been trouble-free, so this isn't a problem with 4TB SSDs in general. We are still working with Samsung to determine the scope and nature of these issues with the 4TB drives, and it is not yet clear whether there is a general compatibility problem or if our testing procedure has triggered a firmware bug that put our samples permanently into an uncooperative mood.

Because of these issues, some benchmark results for the 4TB drives have been delayed. Performance and price notwithstanding, I am unable to recommend any of the 4TB 860 series SSDs until I have a better understanding of the nature of the problems.

The Competition

There are no other consumer QLC SATA SSDs on the market yet, though ADATA has announced their SU630, which will feature alarmingly low capacities. The Intel 660p and Crucial P1 are the only other consumer QLC SSDs currently available, but they are priced for the NVMe market. Most of the competition for the 860 QVO will come from SATA SSDs with TLC NAND, both entry-level models with DRAMless controllers (eg. Toshiba TR200) and more mainstream models like the 860 EVO, Crucial MX500 and WD Blue. Almost all SATA SSD product lines feature a 1TB class model, but there are still relatively few 2TB models and no 4TB competitors have been announced. This will likely change as other QLC drives come to market, and even 2TB TLC drives have been getting more common this year.

AnandTech 2018 Consumer SSD Testbed
CPU	Intel Xeon E3 1240 v5
Motherboard	ASRock Fatal1ty E3V5 Performance Gaming/OC
Chipset	Intel C232
Memory	4x 8GB G.SKILL Ripjaws DDR4-2400 CL15
Graphics	AMD Radeon HD 5450, 1920x1200@60Hz
Software	Windows 10 x64, version 1709
	Linux kernel version 4.14, fio version 3.6
	Spectre/Meltdown microcode and OS patches current as of May 2018

• Thanks to Intel for the Xeon E3 1240 v5 CPU
• Thanks to ASRock for the E3V5 Performance Gaming/OC
• Thanks to G.SKILL for the Ripjaws DDR4-2400 RAM
• Thanks to Corsair for the RM750 power supply, Carbide 200R case, and Hydro H60 CPU cooler
• Thanks to Quarch for the XLC Programmable Power Module and accessories
• Thanks to StarTech for providing a RK2236BKF 22U rack cabinet.

Whole-Drive Fill: Testing SLC Cache Size

This test starts with a freshly-erased drive and fills it with 128kB sequential writes at queue depth 32, recording the write speed for each 1GB segment. This test is not representative of any ordinary client/consumer usage pattern, but it does allow us to observe transitions in the drive's behavior as it fills up. This can allow us to estimate the size of any SLC write cache, and get a sense for how much performance remains on the rare occasions where real-world usage keeps writing data after filling the cache. Samsung's official specifications are:

Samsung 860 QVO Secondary Specifications
Capacity		1 TB	2 TB	4 TB
SLC Cache Size	Min	6 GB	6 GB	6 GB
	Max	42 GB	78 GB	78 GB
Sequential Write	SLC Cache	520 MB/s
	QLC	80 MB/s	160 MB/s	160 MB/s

Our results show the following:

Samsung 860 QVO 1TBSamsung 860 QVO 4TBSamsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBIntel SSD 660p 1TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBToshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

The Samsung 860 QVOs run out of SLC cache right on schedule, at 42 GB for the 1TB model and 78 GB for the 4TB. After that, they are both slow and very steady for the rest of the test.

Average Throughput for last 16 GB	Overall Average Throughput

The 1TB 860 QVO falls below the sequential write speed of a 1TB hard drive once the SLC cache runs out, but the 4TB model is able to sustain twice the write speed and remains ahead of not just the hard drive's speed, but also some of the slower TLC drives.

BAPCo SYSmark 2018

BAPCo's SYSmark 2018 is an application-based benchmark that uses real-world applications to replay usage patterns of business users, with subscores for productivity, creativity and responsiveness. Scores represnt overall system performance and are calibrated against a reference system that is defined to score 1000 in each of the scenarios. A score of, say, 2000, would imply that the system under test is twice as fast as the reference system.

SYSmark scores are based on total application response time as seen by the user, including not only storage latency but time spent by the processor. This means there's a limit to how much a storage improvement could possibly increase scores, because the SSD is only in use for a small fraction of the total test duration. This is a significant difference from our ATSB tests where only the storage portion of the workload is replicated and disk idle times are cut short to a maximum of 25ms.

AnandTech SYSmark SSD Testbed
CPU	Intel Core i5-7400
Motherboard	ASUS PRIME Z270-A
Chipset	Intel Z270
Memory	2x 8GB Corsair Vengeance DDR4-2400 CL17
Case	In Win C583
Power Supply	Cooler Master G550M
OS	Windows 10 64-bit, version 1803

Our SSD testing with SYSmark uses a different test system than the rest of our SSD tests. This machine is set up to measure total system power consumption rather than just the drive's power.

The 860 QVO isn't any slower for compute-heavy interactive tasks than the mainstream SATA SSDs, and even on the more I/O-bound Responsiveness test the 860 QVO is ahead of the DRAMless TLC drive and not far behind the Crucial MX500.

Energy Use

The SYSmark energy usage scores measure total system power consumption, excluding the display. Our SYSmark test system idles at around 26 W and peaks at over 60 W measured at the wall during the benchmark run. SATA SSDs seldom exceed 5 W and idle at a fraction of a watt, and the SSDs spend most of the test idle. This means the energy usage scores will inevitably be very close. A typical notebook system will tend to be better optimized for power efficiency than this desktop system, so the SSD would account for a much larger portion of the total and the score difference between SSDs would be more noticeable.

The Samsung 860 QVO's energy usage during SYSmark is not a problem at all, with it using slightly less energy than the mainstream SATA TLC drives.

AnandTech Storage Bench - The Destroyer

The Destroyer is an extremely long test replicating the access patterns of very IO-intensive desktop usage. A detailed breakdown can be found in this article. Like real-world usage, the drives do get the occasional break that allows for some background garbage collection and flushing caches, but those idle times are limited to 25ms so that it doesn't take all week to run the test. These AnandTech Storage Bench (ATSB) tests do not involve running the actual applications that generated the workloads, so the scores are relatively insensitive to changes in CPU performance and RAM from our new testbed, but the jump to a newer version of Windows and the newer storage drivers can have an impact.

We quantify performance on this test by reporting the drive's average data throughput, the average latency of the I/O operations, and the total energy used by the drive over the course of the test.

The 1TB Samsung 860 QVO does not handle The Destroyer very well, with an average data rate that is slightly slower than the DRAMless TLC drive. By comparison, the NVMe QLC drives from Intel and Micron are only slightly slower than the 860 EVO and MX500.

The QLC drives in general stand out more when looking at latency metrics than throughput, and especially when looking at 99th percentile latencies. The 1TB 860 QVO comes in last place for both average and 99th percentile latency, and all three QLC drives have worse 99th percentile latency than the DRAMless TLC drive.

The average read and write latencies of the 860 QVO are both only slightly worse than the DRAMless TLC SSD. The NVMe QLC drives are slightly faster than the mainstream SATA drives for read latency but fall behind in average write latency.

The 860 QVO actually doesn't come in last place for 99th percentile write latency, and in fact scores far better than the DRAMless TLC drive. However, the QLC drives are all still far worse off than the mainstream TLC SATA drives.

With low performance dragging out the test to a far longer duration, it's no surprise that the QLC drives all use much more energy over the course of The Destroyer than most SATA drives. The DRAMless Toshiba TR200 is an impressive exception that manages to be very efficient despite its low overall performance.

AnandTech Storage Bench - Heavy

Our Heavy storage benchmark is proportionally more write-heavy than The Destroyer, but much shorter overall. The total writes in the Heavy test aren't enough to fill the drive, so performance never drops down to steady state. This test is far more representative of a power user's day to day usage, and is heavily influenced by the drive's peak performance. The Heavy workload test details can be found here. This test is run twice, once on a freshly erased drive and once after filling the drive with sequential writes.

Neither capacity of the Samsung 860 QVO can keep pace with the mainstream TLC drives on the write-intensive Heavy test, but they both outperform the DRAMless TLC drive. The NVMe+QLC drives from Intel and Micron fare much better when the test is run on an empty drive, but when full they too fall behind the mainstream TLC SSDs.

The Samsung 860 QVOs have much worse latency scores than the mainstream TLC drives, and the 99th percentile latency is much worse than even the DRAMless TLC SSD. However, the Samsung QLC drives are a bit better than the Intel/Micron QLC drives at keeping latency under control when the test is run on a full drive.

The average read latencies from the Samsung 860 QVOs are only a bit higher than the mainstream TLC drives, but the average write latencies stand out as worse by at least a factor of two.

The 99th percentile read and write latency scores from the 860 QVOs are poor, but they at least avoid the horrific write QoS issues that the Toshiba TR200 shows, and are better than the full-drive run on the Crucial P1.

The Samsung 860 QVO uses substantially more energy over the course of the Heavy test than the other SATA drives, and more than the the NVMe QLC drives in most cases, too.

AnandTech Storage Bench - Light

Our Light storage test has relatively more sequential accesses and lower queue depths than The Destroyer or the Heavy test, and it's by far the shortest test overall. It's based largely on applications that aren't highly dependent on storage performance, so this is a test more of application launch times and file load times. This test can be seen as the sum of all the little delays in daily usage, but with the idle times trimmed to 25ms it takes less than half an hour to run. Details of the Light test can be found here. As with the ATSB Heavy test, this test is run with the drive both freshly erased and empty, and after filling the drive with sequential writes.

The Samsung 860 QVO has no trouble with the Light test when it is run on an empty drive, and the full-drive performance loss is not too bad: the 1TB 860 QVO remains ahead of the DRAMless TLC drive even when the drives are full.

The average and 99th percentile latency scores from the 860 QVO are no problem when the test is run on a full drive. They're substantially higher when the drives are full, but the latency is better-controlled than on the Intel/Micron QLC drives.

The average read and write latency scores from the 860 QVO are clearly different from the TLC drives for the full-drive test runs, but they don't stand out as significantly worse than what we've seen from some of the slower TLC drives.

The 99th percentile read latency on the 860 QVO is a sore spot when the drive is full, but the 99th percentile write latency doesn't get too far out of control, especially compared to the other two QLC drives.

All of the QLC drives use more energy than the TLC drives during the Light test, and especially when the drives are full and have more background work to do.

Random Read Performance

Our first test of random read performance uses very short bursts of operations issued one at a time with no queuing. The drives are given enough idle time between bursts to yield an overall duty cycle of 20%, so thermal throttling is impossible. Each burst consists of a total of 32MB of 4kB random reads, from a 16GB span of the disk. The total data read is 1GB.

The burst random read performance of the Samsung 860 QVO is clearly lower than the 3D TLC competition, while the Intel/Micron QLC NVMe drives have no trouble competing against the field of mainstream SATA TLC drives. Even in the worst case of the smallest QVO being entirely full, read speeds are still vastly better than a hard drive.

Our sustained random read performance is similar to the random read test from our 2015 test suite: queue depths from 1 to 32 are tested, and the average performance and power efficiency across QD1, QD2 and QD4 are reported as the primary scores. Each queue depth is tested for one minute or 32GB of data transferred, whichever is shorter. After each queue depth is tested, the drive is given up to one minute to cool off so that the higher queue depths are unlikely to be affected by accumulated heat build-up. The individual read operations are again 4kB, and cover a 64GB span of the drive.

On the longer random read test, the Toshiba TR200 DRAMless TLC drive is no longer able to stay ahead of the 860 QVO, and even the Intel/Micron QLC drives fall behind most mainstream SATA drives (especially when full).

Power Efficiency in MB/s/W	Average Power in W

The power consumption of the 860 QVO during the random read test is only slightly higher than its TLC-based relatives, but that's plenty to push its efficiency scores into last place, given the poor performance.

Samsung 860 QVO 1TB Samsung 860 QVO 1TB (Full) Samsung 860 QVO 4TB Samsung 860 QVO 4TB (Full) Samsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBCrucial P1 1000GB (Full)Intel SSD 660p 1TBIntel SSD 660p 1TB (Full drive)Toshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

The queue depth scaling of the 860 QVO during random reads is fairly typical in shape, with improvements starting to taper off after QD16. However, the vertical scale is important: the QVO doesn't ever reach even half the performance of the best TLC-based SATA SSDs.

Looking at the 1TB 860 QVO's random read results compared to all the other SATA drives in the benchmark database, it is clear that the QVO isn't anywhere near the cutting edge for power efficiency or peak performance, but there are worse drives out there.

Random Write Performance

Our test of random write burst performance is structured similarly to the random read burst test, but each burst is only 4MB and the total test length is 128MB. The 4kB random write operations are distributed over a 16GB span of the drive, and the operations are issued one at a time with no queuing.

The SLC cache of the 860 QVO is very effective for the burst random write test, leaving it tied or slightly ahead of the 860 EVO.

As with the sustained random read test, our sustained 4kB random write test runs for up to one minute or 32GB per queue depth, covering a 64GB span of the drive and giving the drive up to 1 minute of idle time between queue depths to allow for write caches to be flushed and for the drive to cool down.

On the longer random write test, the larger SLC cache and greater parallelism of the 4TB 860 QVO helps it keep pace with other top SATA SSDs, but the 1TB QVO has to settle for being slightly faster than the DRAMless TLC drive.

Power Efficiency in MB/s/W	Average Power in W

The QVO is again a bit more power hungry than most of the TLC drives, which doesn't hurt the 4TB QVO's efficiency score much thanks to its good performance, but the 1TB QVO ends up tied for last place with the full-drive performance from the Intel/Micron QLC drives.

Samsung 860 QVO 1TBSamsung 860 QVO 1TB (Full)Samsung 860 QVO 4TB Samsung 860 QVO 4TB (Full) Samsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBCrucial P1 1000GB (Full)Intel SSD 660p 1TBIntel SSD 660p 1TB (Full drive)Toshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

The 1TB 860 QVO shows very little random write performance scaling with increasing queue depth, though power consumption does go up significantly from QD1 to QD2. The 4TB 860 QVO shows a much more typical scaling up to saturation at QD4, with a performance curve that is almost an exact match for the 4TB 860 EVO.

There are some TLC SATA SSDs that draw the same power to deliver half the random write performance of the 1TB 860 QVO, but in the grand scheme of things the 1TB QVO's results on this test are sub-par. The 4TB starts out in the same spot but ends up hitting the SATA performance wall without consuming too much power.

Sequential Read Performance

Our first test of sequential read performance uses short bursts of 128MB, issued as 128kB operations with no queuing. The test averages performance across eight bursts for a total of 1GB of data transferred from a drive containing 16GB of data. Between each burst the drive is given enough idle time to keep the overall duty cycle at 20%.

The burst sequential read performance of the Samsung 860 QVO is generally competitive with mainstream TLC SATA SSDs and is well ahead of the DRAMless Toshiba TR200. The 1TB 860 QVO's score is a bit lower when the drive isn't full because of the timing of the tests: the drive was still flushing the SLC cache in the background when the read test started.

Our test of sustained sequential reads uses queue depths from 1 to 32, with the performance and power scores computed as the average of QD1, QD2 and QD4. Each queue depth is tested for up to one minute or 32GB transferred, from a drive containing 64GB of data. This test is run twice: once with the drive prepared by sequentially writing the test data, and again after the random write test has mixed things up, causing fragmentation inside the SSD that isn't visible to the OS. These two scores represent the two extremes of how the drive would perform under real-world usage, where wear leveling and modifications to some existing data will create some internal fragmentation that degrades performance, but usually not to the extent shown here.

On the longer sequential read test, the 860 QVO continues to get reasonably close to the SATA speed limit when reading data that is contiguous on the flash itself. Where internal fragmentation is caused by writing to the drive randomly, the QVO's read speed suffers much more than for the TLC drives, and the 1TB 860 QVO ends up slightly slower than a mechanical hard drive.

Power Efficiency in MB/s/W	Average Power in W

The power efficiency of the 860 QVO is only a little bit lower than the TLC drives for the contiguous data case. When dealing with fragmented data, the QVO is slightly more efficient than the Intel/Micron NVMe QLC drives despite being a bit slower.

Samsung 860 QVO 1TBSamsung 860 QVO 1TB (Full)Samsung 860 QVO 4TB Samsung 860 QVO 4TB (Full) Samsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBCrucial P1 1000GB (Full)Intel SSD 660p 1TBIntel SSD 660p 1TB (Full drive)Toshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

The queue depth scaling behavior for the 860 QVO is very typical, with QD1 not quite saturating the SATA link but all higher queue depths hitting close to full speed. The one exception is a slight decrease from the 1TB drive during the final QD32 phase.

Aside from the mild QD32 drop in performance, the sequential read behavior of the 860 QVO doesn't fall outside the normal ranges we've come to expect from TLC drives.

Sequential Write Performance

Our test of sequential write burst performance is structured identically to the sequential read burst performance test save for the direction of the data transfer. Each burst writes 128MB as 128kB operations issued at QD1, for a total of 1GB of data written to a drive containing 16GB of data.

The Samsung 860 QVO handles the burst sequential write test fine when the drive is mostly empty and there's plenty of room in the SLC cache. When the drive is full, the 1TB model's speed suffers somewhat, but is still much faster than the mechanical hard drive or the DRAMless TLC drive.

Our test of sustained sequential writes is structured identically to our sustained sequential read test, save for the direction of the data transfers. Queue depths range from 1 to 32 and each queue depth is tested for up to one minute or 32GB, followed by up to one minute of idle time for the drive to cool off and perform garbage collection. The test is confined to a 64GB span of the drive.

On the longer sequential write test, the SLC cache of the 1TB 860 QVO is not quite enough even when the drive is mostly empty, so it ends up in last place. The 4TB model's SLC cache keeps up with this test and it is as fast as any SATA drive.

Power Efficiency in MB/s/W	Average Power in W

The 860 QVO is a bit more power-hungry than the 860 EVO, so the 4TB QVO only takes third place for efficiency among the SATA drives in this bunch. The 1TB QVO has similar efficiency to the faster but more power-hungry 1TB QLC NVMe drives from Intel and Micron.

Samsung 860 QVO 1TBSamsung 860 QVO 1TB (Full)Samsung 860 QVO 4TB Samsung 860 QVO 4TB (Full) Samsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBCrucial P1 1000GB (Full)Intel SSD 660p 1TBIntel SSD 660p 1TB (Full drive)Toshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

The 1TB 860 QVO is mostly slow and steady during the sequential write test, while the 4TB model's performance is as good as any other SATA drive.

The 1TB 860 QVO's sequential write behavior sticks out clearly as far slower than typical, but it's not unprecedented: there have been TLC drives this slow, but most of them were much smaller than 1TB. The 4TB model blends in with the crowd much better.

Mixed Random Performance

Our test of mixed random reads and writes covers mixes varying from pure reads to pure writes at 10% increments. Each mix is tested for up to 1 minute or 32GB of data transferred. The test is conducted with a queue depth of 4, and is limited to a 64GB span of the drive. In between each mix, the drive is given idle time of up to one minute so that the overall duty cycle is 50%.

The Samsung 860 QVO's performance on the mixed random I/O test is substantially slower than the 860 EVO, but it is not far behind some of the other mainstream TLC drives. Running the test on a full drive does slow the 1TB 860 QVO down significantly, but it remains faster than the DRAMless TLC drive.

Power Efficiency in MB/s/W	Average Power in W

The power efficiency rankings for the 860 QVO aren't much better than the raw performance rankings. Power consumption is generally a bit higher than the 860 EVO but doesn't vary much with capacity or state of fill, so the efficiency scores are largely reflective of the performance variations.

Samsung 860 QVO 1TBSamsung 860 QVO 1TB (Full)Samsung 860 QVO 4TB Samsung 860 QVO 4TB (Full) Samsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBCrucial P1 1000GB (Full)Intel SSD 660p 1TBIntel SSD 660p 1TB (Full drive)Toshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

The 860 QVO starts out with a fairly slow random read speed but steadily speeds up as the workload shifts toward writes, eventually catching up to the 860 EVO. When the test is run on a full drive, the 1TB 860 QVO runs out of SLC cache in the final few phases of the test and slows down instead of continuing to speed up.

Mixed Sequential Performance

Our test of mixed sequential reads and writes differs from the mixed random I/O test by performing 128kB sequential accesses rather than 4kB accesses at random locations, and the sequential test is conducted at queue depth 1. The range of mixes tested is the same, and the timing and limits on data transfers are also the same as above.

The 4TB 860 QVO handles the mixed sequential I/O test well, but the 1TB model ends up slightly slower than the DRAMless TLC drive and well behind the mainstream TLC drives.

Power Efficiency in MB/s/W	Average Power in W

The power efficiency scores vary more among the SATA drives than the raw performance scores, so the 860 EVO and Toshiba TR200 stand out as particularly efficient while the 860 QVO 4TB is merely average and the 1TB model is struggling a bit.

Samsung 860 QVO 1TBSamsung 860 QVO 1TB (Full)Samsung 860 QVO 4TB Samsung 860 QVO 4TB (Full) Samsung 850 PRO 1TBSamsung 860 EVO 1TBSamsung 860 EVO 4TBCrucial MX300 2050GBCrucial MX500 1TBCrucial P1 1000GBCrucial P1 1000GB (Full)Intel SSD 660p 1TBIntel SSD 660p 1TB (Full drive)Toshiba TR200 960GBWD Black 7200RPM 1TBWD Blue 1TB 3D NAND

Both capacities of the 860 QVO offer decent performance at either end of the test with pure reads or pure writes, and they are unsurprisingly at their worst with the more write-heavy mixes. The 1TB 860 QVO loses far more performance across the first two thirds of the test, but catches back up with the 4TB model at the end.

Idle Power Measurement

SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.

Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.

We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled if supported.

It appears that the 1TB Samsung 860 QVO was still busy with background processing several minutes after the test data was written to the drive, so our automated idle power measurement caught it still drawing 2W. The 4TB was much quicker to flush its SLC cache and turned in a respectable active idle power consumption score. Both drives have good idle power consumption when put into the slumber state, though we've measured slightly higher than the official spec of 30mW.

The wake-up latency for the 860 QVO is the same as their other SATA SSDs, hovering around a reasonable 1.2 ms. It's not the best that can be achieved over SATA, but it's nothing to complain about.

Conclusion

The Samsung 860 QVO is not the first consumer QLC SSD we've tested, but in many ways it better conforms to our expectations for QLC than the Intel 660p and Crucial P1 did. Those NVMe SSDs don't do much to satisfy demand for a cheap entry-level drive or for a high-capacity drive, the two applications where QLC NAND seems most useful. QLC has been pitched to us several times as a HDD replacement, rather than a performance product. It was a bit of a surprise to see QLC first arrive in NVMe SSDs. By contrast, the 860 QVO is an extremely predictable product with no surprises whatsoever in its design. Samsung is building on a tried and true formula, just adapting the 860 EVO to work with QLC NAND.

QLC NAND is fundamentally about sacrificing quality for quantity. The viability of QLC SSDs rests on the assumption that existing drives are more than fast enough, which is something that's certainly true of many Samsung SSDs. The Samsung 860 QVO is not as fast or as power efficient as the 860 EVO, but it doesn't need to be. Samsung has tended to stay out of the true entry-level segment of the SSD market, and there's been room for something like the QVO in their product lineup for much longer than they've had the technology to make a QLC SSD.

As with the other two QLC drives we've tested, the important takeaway is that the use of QLC NAND does not have a revolutionary impact on the final product. The 860 QVO is still suitable for general-purpose consumer storage duty. It is slower than the 860 EVO, but the QVO is far from the slowest SATA SSD we've tested. Thanks to a combination of SLC caching and the SATA link bottleneck, the 860 QVO's behavior is often indistinguishable from other SATA SSDs. Based on benchmark results alone, it would be difficult to conclusively identify the QVO as a QLC-based drive, rather than just a relatively slow TLC drive. The true giveaways are the sustained write performance after the SLC cache is full, and the amount of idle time required for the drive to recover after using up its write cache. Neither of those scenarios are a common occurrence during typical consumer usage.

From a technological perspective, QLC NAND seems to be ready to make an impact on the consumer storage market. It's fast enough to still be a huge step up from hard drives, and the write endurance is still adequate. Samsung should be commended for only offering the 860 QVO in 1TB and larger capacities. The competitors that use QLC in smaller drives will be facing downsides that are much harder to overlook. Even as they introduce a lower tier, Samsung is keeping their products out of the gutter.

With the Intel and Micron QLC drives using NVMe to the 860 QVO's SATA, there's a lot to get in the way of comparing Samsung's QLC to Intel/Micron QLC. From our testing so far, there doesn't seem to be a clear winner. Tests where the 860 QVO hits the limits of the SATA interface aren't helpful. Among the other tests, the Intel/Micron QLC seems to generally be a bit faster, but some of that is still due to the NVMe interface. Power efficiency seems to be broadly similar between the two QLC designs.

SATA SSD Price Comparison
	250GB	500GB	1TB	2TB	4TB
Samsung 860 QVO (MSRP)			$149.99 (15¢/GB)	$299.99 (15¢/GB)	$599.99 (15¢/GB)
Samsung 860 EVO	$55.99 (22¢/GB)	$72.99 (15¢/GB)	$127.98 (13¢/GB)	$294.88 (15¢/GB)	$797.99 (20¢/GB)
Samsung 860 PRO	$97.00 (38¢/GB)	$147.00 (29¢/GB)	$284.99 (28¢/GB)	$577.99 (28¢/GB)	$1179.99 (29¢/GB)
Toshiba TR200	$39.99 (17¢/GB)	$79.99 (17¢/GB)	$274.89 (29¢/GB)
WD Blue 3D NAND	$53.00 (21¢/GB)	$77.99 (16¢/GB)	$134.99 (13¢/GB)	$322.99 (16¢/GB)
Crucial MX500	$52.51 (21¢/GB)	$74.99 (15¢/GB)	$139.99 (14¢/GB)	$325.99 (16¢/GB)
Seagate Barracuda	$58.99 (24¢/GB)	$84.99 (17¢/GB)	$149.99 (15¢/GB)	$349.99 (17¢/GB)
Micron 1100				$284.25 (14¢/GB)
NVMe:
Intel 660p		$74.99 (15¢/GB)	$169.99 (17¢/GB)
Crucial P1		$104.13 (21¢/GB)	$219.99 (22¢/GB)

The downsides of QLC NAND—be they mild or severe—are all accepted in exchange for the promise of affordability. Other things being equal, QLC NAND should ideally be 25% cheaper than TLC NAND. There are several reasons why this is an unobtainable goal at this point, but even accounting for those, the few QLC SSDs we have so far are all failing to deliver the improved affordability. NAND flash memory prices are dropping across the board, so now is not the best time to try to use new technology to get ahead on pricing. The 860 QVO looks likely to suffer the same fate that affects many entry-level DRAMless SATA SSDs: the higher-volume mainstream SSDs are on the leading edge of the price drops, and that means they often close the gap with entry-level SSDs.

Samsung's MSRPs for the 860 QVO reflect that. The current street prices for the 860 EVO are lower than the 860 QVO for two out of three capacities, and that's comparing against one of the best SATA SSDs out there. There are plenty of mainstream drives with slightly lower performance. The exception is in the 4TB segment where Samsung is unopposed. The 4TB segment is only just now starting to look viable, but at $600 for the 4TB QVO it is still well out of a normal consumer price range. It might be worth revisiting the 860 QVO in a few months on pricing to see where it stands.

Samsung plans for the 860 QVO to be available for purchase starting December 16. By then, the holiday sale pricing and related shortages should have settled down, and Samsung will have had the chance to re-consider their pricing. In the meantime, the 860 EVO remains the obviously superior choice.