The latest entry level SSD from Samsung has no suffix and bears neither the PRO or EVO appellation. It is a new entry-level SATA SSD featuring Samsung's latest 64-layer 3D TLC NAND, making it a very close relative to the 850 EVO line.

The Samsung SSD 850 120GB Review: A Little TLC for SATA

The SSD 850 120GB uses the same MGX controller as the 850 EVO, but with a newer generation of 3D NAND. The drive is intended to fill a gap that has existed in Samsung's retail product line since the 750 EVO was discontinued a little over a year ago, as it left Samsung with no 120GB-class retail SSD. So far, the SSD 850 120GB has only been officially released by Samsung's Chinese division, but it is available in other Asian markets including from some online retailers that will ship to us in North America. The release it seems will be staggered across regions.

The Samsung 750 EVO was a stopgap product, using 16nm planar TLC, while the 850 family transitioned from 32-layer to 48-layer 3D NAND. That transition for the 850 series doubled the capacity per die, from 128Gb to 256Gb. With half as many dies to use in parallel, the smallest capacities of the 850 PRO and EVO would no longer meet the same performance specifications. Changing components like this without renaming the product can be controversial, but Samsung took the reasonable route of discontinuing the 128GB 850 PRO and 120GB 850 EVO. It was their hope that the 120GB capacity class would be rendered mostly obsolete by the price/GB improvements enabled by denser 3D NAND.

When Samsung's 48L 3D NAND initially failed to reach its production or price targets, it became clear that Samsung still needed an affordable 120GB-class drive in its retail lineup. The 750 EVO was introduced to fill that gap, using 16nm TLC but retaining the same top-notch SSD controller from the 850 series. The 750 EVO initially debuted with 120GB and 250GB capacities, but a 500GB version was added as SSD prices began to rise across the industry due to a global shortage of NAND flash memory. (The disappointments of Samsung's 48L 3D NAND were one of the major supply-side factors leading to the shortage, but insatiable demand for SSDs and the difficulties everyone else had bringing any kind of 3D NAND to market were also very important contributors.) By the end of 2016, SSD prices were still rising but Samsung quietly discontinued the 750 EVO, again leaving them with a gap at the smallest end of the capacity range.

The Samsung SSD 850 120GB is a product that Samsung never wanted to release, and it may even never see a global release. The fundamental challenge of offering 850 EVO-class performance on a drive with just four NAND flash dies hasn't gone away. Samsung's 64L 3D NAND is claimed to be a bit faster than the 48L NAND for writes, and power consumption is supposed to be lower for both reads and writes. This won't do much to offset the effects of limited parallelism with only four NAND dies.

Samsung TLC SATA SSD Comparison
Drive	850 120GB		750 EVO 120GB	850 EVO 120GB
Launch	China: Nov 2017		April 2016	December 2014
Controller	Samsung MGX		Samsung MGX	Samsung MGX
NAND	Samsung 256Gb 64L TLC V-NAND		Samsung 128Gb 16nm TLC	Samsung 128Gb 32L TLC V-NAND
DRAM	256 MB		256 MB	256 MB
Sequential Read	540 MB/s		540 MB/s	540 MB/s
Sequential Write	520 MB/s		520 MB/s	520 MB/s
4KB Random Read	70k IOPS		94k IOPS	94k IOPS
4KB Random Write	88k IOPS		88k IOPS	88k IOPS
4KB Random Read QD1	10k IOPS		10k IOPS	10k IOPS
4KB Random Write QD1	40k IOPS		35k IOPS	40k IOPS
Encryption	AES-256, TCG Opal 2.0, IEEE-1667 (eDrive)		AES-256, TCG Opal 2.0, IEEE-1667 (eDrive)	AES-256, TCG Opal 2.0, IEEE-1667 (eDrive)
Endurance	75TB or 100TB		35TB	75TB
Warranty	Three years		Three years	Five years

Like the 750 EVO, the Samsung SSD 850 120GB inherits all the 850 EVO's features like TCG Opal support thanks to using the same controller, but the 850 120GB's three year warranty is shorter than the five years on the 850 EVOs. The write endurance is thankfully on par with or better than the old 120GB 850 EVO (Samsung China's site is inconsistent about this specification), whereas the 750 EVO had less than half the write endurance. The only performance specification where the 850 120GB is slower than the old 850 EVO 120GB is for random reads at QD32, where it has lost 25% of the peak performance. However, performance numbers on the box like these do not tell the whole story.

A Lot of Empty Space

The Samsung S4LN062X01 "MGX" controller in the 850 120GB is old news. After three years on the market in the 850 EVO and related OEM and enterprise SSDs, it's still one of the top SATA SSD controllers with all the expected features and great performance and power management.

While the 750 EVO put the controller and DRAM in the same BGA package, the 850 uses the original controller packaging with the DRAM next to it on the circuit board. The Samsung SSD 850 120GB uses the same PCB as current 850 EVOs up to 500GB, with one of the two NAND package spots populated, and the case is Samsung's standard matte black metal secured with three pentalobe screws.

Samsung's NAND flash part numbers don't directly encode the manufacturing process used. The sole NAND package on the 850 120GB is marked K9CKGY8H5A. The "CKG" portion identifies this as a TLC package with four dies and a total capacity of 128GB, implying the use of 256Gb (32GB) dies. The "A" at the end of the part number designates this as Samsung's second generation of 256Gb TLC parts. The first generation of 256Gb TLC dies from Samsung was manufactured with their 48-layer V-NAND process, making this new part their 64-layer design. When Samsung gets around to shipping their 512Gb 64L TLC dies, they'll be marked with a "M" at the end of the part number because they are Samsung's first generation 512Gb TLC parts.

This isn't our first encounter with Samsung's 64-layer fourth-generation 3D NAND. The Samsung Portable SSD T5 launched earlier this year as the first product to feature the 64L TLC V-NAND. Samsung used a portable SSD as the trial run for their preceding 48-layer 3D NAND as well, followed by a gradual migration of the rest of the product line. Samsung hasn't stated whether they plan to migrate the 850 EVO line over to 64L TLC in the same manner as they transitioned it from 32L to 48L, but I suspect they will. SATA SSDs aren't going away any time soon, and the current 850 EVOs are already competitive with the 64L 3D TLC SSDs from Western Digital/SanDisk and Intel. Updating the 850 EVO with 64L 3D TLC won't hurt the small capacity models because the capacity per die remains 256Gb.

The future of the 850 PRO line and MLC drives in general is less clear. Samsung has said nothing about 64L MLC and even their enterprise SSDs are all on TLC now (except for the Z-NAND based SZ985). The 850 PRO has very little reason to continue existing now that NVMe drives are the high-performance option, so Samsung may end up discontinuing it and simplifying their retail SATA line to just a range of TLC-based 850s, starting with this 120GB model. In the NVMe space they will probably keep a MLC model around for enthusiasts unless their next generation of TLC-based NVMe SSDs can deliver huge performance increases. We expect Samsung to officially disclose some of their plans early next year, either at CES or shortly thereafter.

There isn't much competition in the 120GB capacity class of SSDs. Other manufacturers have also largely abandoned this segment as they transition to 3D NAND with per-die capacities of 256Gb and larger. The only recent SSDs we have to compare against are a few drives using Micron's 384Gb 32L 3D TLC NAND. The first two, the ADATA Ultimate SU800 and the HP S700 Pro, pair that Micron NAND with the Silicon Motion SM2258 controller, while the other member of the set is the HP S700, which adopts the DRAMless SM2258XT controller. The rest of the 120GB-class drives we have tested are all discontinued: the Samsung 850 PRO 128GB, the Samsung 850 EVO 120GB, the Samsung 750 EVO 120GB, the ADATA SP550 using planar TLC, the PNY CS1311 also using planar TLC, and the ADATA XPG SX930 which uses planar MLC and a JMicron controller.

The glaring omission from this review is the Crucial BX300. Micron used their 3D MLC for this model specifically designed to perform well at low capacities, but then they only sampled us the largest size to test. The 120GB BX300 is currently priced very well for a 120GB drive even before taking into account that it uses 3D MLC instead of TLC. It's also readily available for purchase in most markets. Based on the results at higher capacities, we expect the 120GB BX300 to be slightly below 

AnandTech 2017 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 1703
	Linux kernel version 4.12, fio version 2.21

• 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

Not all of our regular benchmarks are performed in this review to begin with. Our test called 'The Destroyer' is slightly delayed - on the first run through, the SSD 850 returned suspiciously low scores, so it is currently being re-run. ATSB on the 2017 testbed for a few other 120GB drives were also not at hand due the drives being in service as boot drives on other testing machines. The page of results for The Destroyer will be added later today (11/27).

AnandTech Storage Bench - Heavy

Our Heavy storage benchmark is proportionally more write-heavy than our heaviest in-house tests, 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.

The average data rate of the Samsung SSD 850 120GB on the Heavy test is slightly faster than the discontinued 850 EVO 120GB, but nowhere near the performance of the 850 PRO 128GB. The drives using Silicon Motion controllers and Micron 3D TLC offer less than half the speed of the 850 120GB.

The average and 99th percentile latency scores of the 850 120GB are very similar to the discontinued 850 EVO 120GB, but slightly faster. The 850 PRO 128GB and the larger 250GB 850 EVO are faster, and the 250GB EVO in particular shows less of a performance impact when the test is run on a full drive, but in all cases the Samsung drives offer lower latency than the Micron-based drives.

The average read and write latencies of the 850 120GB are slightly faster than the 850 EVO 120GB. The write latencies show more variation between drives than the read latencies, and the write latencies are much higher than the read latencies.

The 850 120GB has slightly worse 99th percentile read latency than the 850 EVO when the test is run on an empty drive, but better 99th percentile read latency when the drives are full. The situation is reversed for 99th percentile write latency, but both the SSD 850 and 850 EVO drives still have a lower latency than the 750 EVO.

AnandTech Storage Bench - Light

Our Light storage test has relatively more sequential accesses and lower queue depths than 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 SSD 850 120GB manages to deliver an average data rate that is slightly higher than even the 128GB 850 PRO on the Light test, when the drives are empty. On a full drive, the 850 PRO retakes the lead.

The average and 99th percentile latencies of the Samsung 850 120GB are not the best, but like the other Samsung drives it doesn't experience a catastrophic breakdown of performance when full. The drives using Micron 3D TLC all lose control over latency.

The 850 120GB shows a substantial difference in average read latency between test runs with a full or empty drive. The average write latency is completely unaffected, while the Micron 3D TLC drives end up stalling write commands when their write buffers overflow.

The 99th percentile latency figures further emphasize the difference in behavior between the Samsung drives and the SMI+Micron drives. All of them perform fine in ideal conditions, but the Samsungs are much better at handling the pressure of operating while full. The 850 PRO 128GB and the 850 EVO 250GB show a much smaller impact to read latency than the 850 120GB and the other two Samsung 120GB TLC drives.

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 Samsung SSD 850 120GB has a significantly slower random read speed than its predecessors from Samsung, but it is still faster than any other brand. The Micron 3D TLC-based SSDs that are actually currently for sale are the three slowest drives on this test.

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 that brings in higher queue depths, the rankings are almost unchanged. The 850 120GB is Samsung's slowest, but everyone else is much slower.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

At higher queue depths, the Samsung drives scale up to much higher performance levels than the competing 120GB-class SSDs. The 850 is still the slowest of Samsung's drives and it falls short by more than 100MB/s at QD16 and higher, but by that point the 850 is 2.5 times faster than the quickest Micron 3D TLC-based drive.

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.

There aren't huge disparities between the 120GB-class SSDs on the burst random write test, save for the DRAMless HP S700. The Samsung SSD 850 is only slightly slower than the old 850 EVO, but two of the drives using Micron 3D TLC come out on top for this test.

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.

With a longer test duration that will tend to fill the whatever SLC write cache such a small drive can include, the old Samsung 850 PRO 128GB is unsurprisingly the winner by a wide margin. The Samsung 850 comes in second place and slightly ahead of the old 850 EVO, somewhat corroborating Samsung's claims that their 64L 3D TLC offers improved write performance.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

The performance of the Samsung 850 holds up through most of the random write test, but doesn't improve significantly as queue depths grow. By the end of the test, the drive has fallen behind on garbage collection despite the idle time it is allowed between queue depths, and performance drops off. Most of the other drives suffer a similar fate at some point during the test; the 750 EVO is the fastest drive that doesn't show a precipitous drop at any point. The Samsung 850 PRO was still faster than the rest even after its spare area was filled and it was forced to perform garbage collection through the later parts of the test.

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 SSD 850 120GB places it in the second tier of 120GB-class drives, but it's actually the fastest of the current models. The performance is a clear improvement over the 850 EVO but is about the same as the 750 EVO and the HP S700.

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.

On the longer test of sequential reads, the Samsung 850 falls well below the standard set by Samsung's earlier drives and ends up slightly slower than the HP S700. The S700 Pro and ADATA SU800 are in last place with less than half the performance of the 850 120GB.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

Most drives show no performance scaling with queue depth on the sequential read test. The older Samsung drives all show some improvement from QD1 to QD2 and are steady after that, while the 850 120GB is simply the same speed across the board.

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 short burst sequential write speed of the Samsung SSD 850 120GB is comparable to Samsung's other drives in this capacity class, and is better than any other current drive for this segment.

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 Samsung SSD 850 120GB is tied for second place, though the performance of the 850 PRO far outshines everything else.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

As with sequential reads, most of these drives handle sequential writes at the same speed regardless of queue depth. The 850 PRO is the only one to show substantial improvement as queue depths increase. Several other drives experience temporary hits to their write performance as a result of their SLC write caches filling and forcing the drive to perform garbage collection, but most are steady through most of the test.

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 mixed random I/O performance of the Samsung SSD 850 120GB is substantially slower than the old 850 EVO, but is slightly faster than the 750 EVO and well ahead of all the non-Samsung drives.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

The 850 120GB isn't particularly consistent across the mixed random I/O test, and there isn't a strong trend to its performance. It is somewhat slower on the write-heavy half of the test. It is slower than the old 850 EVO in every phase of the test and doesn't significantly pick up the pace at the end when the workload is almost pure random writes, but neither does it suffer any severe performance drops.

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 Samsung drives are the four fastest drives on the mixed sequential workload test, with the 850 120GB coming in third place of the 120-128GB drives and only slightly faster than the 750 EVO. The 850 120GB is about 30% faster than the HP S700, the next fastest in-production model in this roundup.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

The performance of the Samsung SSD 850 120GB drops significantly during the first half of the mixed sequential I/O test as the proportion of writes increases, but it stabilizes in the second half of the test. The other Samsung drives are the only ones that meaningfully outperform the 850 120GB at any point during the test,
but the 850 PRO is the only one that maintains a clear lead over the 850 120GB all the way through.

Conclusion: It's a Good Option at 120GB

There are few options for a decent 120GB class SSD in today's market. For the most part, modern NAND flash chips have simply outgrown this market segment. Entry-level drives are almost always based on TLC NAND, and that means relatively few high-capacity dies. The drives are also strongly dependent on SLC write caching for offering the best peak performance, but a 120GB drive doesn't have room for much cache. Every 120GB-class drive carries a steep price/GB premium over the next size up, such as $50 for 120GB and $70 for 240GB.

The Samsung SSD 850 120GB can't overcome all of those handicaps, but it comes close. Overall performance is on par with or better than the discontinued Samsung 850 EVO 120GB, though the two have slightly different strengths and weaknesses. Samsung's dominance is clear from the number of tests where all of the Samsung drives outperform all of the competing TLC-based 120GB-class SSDs. But these are still all low-end drives. A 250GB class drive will be significantly faster and offer far more storage for the money. The Samsung SSD 850 120GB is one of the better choices out of a mediocre pool, but most users should opt for a 240GB or larger drive instead.

If Samsung wanted to brand the 850 120GB as a full member of the 850 EVO family, it would be worthy. We can't really expect any better performance from a drive this size, and Samsung can probably afford to extend the warranty to match the 5 years offered with other 850 EVOs. So far, the 850 120GB has seen limited release in Asia, but it's suitable for a global release, provided the price is right. Measured against today's steep discounts for Cyber Monday, the SSD 850 120GB could fit in to the US market somewhere around $60.