During the early days of SSDs, we saw rather quick development in capacities. The very first SSDs were undoubtedly small, generally 32GB or 64GB, but there was a need for higher capacities to make SSDs more usable in client environments. MLC NAND caused a rapid decline in prices and the capacities quickly increased to 128GB and 256GB. 512GB also came along fairly soon, but for a long while the 512GB drives cost more than a decent gaming PC with prices being over $1000.

I would argue that the 512GB drives were introduced too early - the adoption was minimal due to the absurd price. The industry learned from that and instead of pushing 1TB SSDs to the market at over $1000, it wasn't until 2013 when Crucial introduced the M500 with the 960GB model being priced reasonably at $600. Nowadays 1TB has become a common capacity in almost every OEM's lineup, which is thanks to both lower NAND prices and controllers being sophisticated enough to manage 1TB of NAND. The next milestone is obviously the multi-terabyte era, which we are entering with the release of 2TB Samsung 850 Pro and EVO models.

Breaking capacity thresholds involves work on both the NAND and the controller side. All controllers have a fixed number of die they can talk to and for modern 8-channel controllers with eight chip enablers (CEs) per channel the limit is typically 64 dies. With 128Gbit (16GB) being the common NAND die capacity today, 64 dies yields 1,024GB or 1TB (as it's often marketed). It's possible to utilize a single CE for managing more than one die (which is what e.g. Silicon Motion does to achieve 1TB with a 4-channel controller), but it adds complexity to the firmware design and there's a negative performance impact as the two dies on the same chip enabler can't be accessed simultaneously. 

Increasing NAND capacity per die is one way to work around the channel/CE limitation, but it's generally not the most efficient way. First off, doubling the capacity of the die increases complexity substantially because you are effectively dealing with twice the number of transistors per die. The second drawback is reduced write performance, especially at smaller capacities, as SSDs rely heavily on parallelism for performance, so doubling the capacity per die will cut parallelism in half. That reduces the usability of the die in capacity sensitive applications such as eMMC storage, which don't have many die to begin with (as the same dies are often used in various different applications ranging from mobile to enterprise).

The new MHX controller

The real bottleneck, however, is the DRAM controller. Today's NAND mapping table designs tend to require about 1MB of DRAM per 1GB of NAND for optimal performance, so breaking the 1TB limit requires a DRAM controller capable of supporting 2GB of DRAM. From a design standpoint, implementing a beefier DRAM controller isn't a massive challenge, but it eats both die and PCB area and hence increases cost. Given how 2TB SSDs are currently a relatively small niche, embedding a DRAM controller with 2GB support for a mainstream controller isn't very economical, which is why today's client-grade SSD controller usually support up to 1GB to increase cost efficiency. 

Initially the 850 EVO was supposed to carry a 2TB SKU at the time of launch, but Samsung didn't consider the volume to be high enough. As Samsung is the number one manufacturer of client SSDs and supplies millions of drives to PC OEMs, the company is not really in the business of making low volume niche products, hence the release of 2TB client SSDs was postponed in wait for lower pricing and higher demand as a result.

Comparison of Samsung SSD Controllers
	MDX	MEX	MGX	MHX
Core Architecture	ARM Cortex R4
# of Cores	3	3	2	3
Core Frequency	300MHz	400MHz	550MHz	400MHz
Max DRAM	1GB	1GB	512MB (?)	2GB
DRAM Type	LPDDR2	LPDDR2	LPDDR2	LPDDR3

The new 2TB versions of the 850 Pro and EVO both use Samsung's new MHX controller. I was told it's otherwise identical to the MEX besides the DRAM controller supporting up to 2GB of LPDDR3, whereas the MEX only supports 1GB of LPDDR2. The MGX is the lighter version of MEX with two higher clocked cores instead of three slower ones, and it's found in the 120GB, 250GB and 500GB EVOs.

Samsung SSD 850 Pro Specifications
Capacity	128GB	256GB	512GB	1TB	2TB
Controller	MEX				MHX
NAND	Samsung 32-layer MLC V-NAND
NAND Die Capacity	86Gbit				128Gbit
DRAM	256MB	512MB	512MB	1GB	2GB
Sequential Read	550MB/s	550MB/s	550MB/s	550MB/s	550MB/s
Sequential Write	470MB/s	520MB/s	520MB/s	520MB/s	520MB/s
4KB Random Read	100K IOPS	100K IOPS	100K IOPS	100K IOPS	100K IOPS
4KB Random Write	90K IOPS	90K IOPS	90K IOPS	90K IOPS	90K IOPS
DevSleep Power	2mW				5mW
Slumber Power	Max 60mW
Active Power (Read/Write)	Max 3.3W / 3.4W
Encryption	AES-256, TCG Opal 2.0 & IEEE-1667 (eDrive supported)
Endurance	150TB		300TB
Warranty	10 years

Specification wise the 2TB 850 Pro is almost identical to its 1TB sibling. The performance on paper is an exact match with the 2TB model drawing a bit more power in DevSleep mode, which is likely due to the additional DRAM despite LPDDR3 being more power efficient than LPDDR2. Initially the 850 Pro was rated at 150TB of write endurance across all capacities, but Samsung changed that sometime after the launch and the 512GB, 1TB and 2TB versions now carry 300TB endurance rating along with a 10-year warranty.

There's another hardware change in addition to the new MHX controller as the NAND part number suggests that the 2TB 850 Pro uses 128Gbit dies instead of the 86Gbit dies found in the other capacities. The third character, which is a U in this case, refers to the type of NAND (SLC, MLC or TLC) and the number of dies, and Samsung's NAND part number decoder tells us that U stands for a 16-die MLC package. With eight NAND packages on the PCB, each die must be 128Gbit (i.e. 16GiB) to achieve raw NAND capacity of 2,048GiB. 2,048GB out of that is user accessible space, resulting in standard ~7% over-provisioning due to GiB (1024^3 bytes) to GB (1000^3 bytes) translation.

According to Samsung, this is still a 32-layer die, which would imply that Samsung has simply developed a higher capacity die using the same process. It's logical that Samsung decided to go with a lower capacity die at first because it's less complex and yields better performance at smaller capacities. In turn, a larger die results in additional cost savings due to peripheral circuitry scaling, so despite still being a 32-layer part the 128Gbit die should be more economical to manufacture than its 86Gbit counterpart.

Samsung SSD 850 EVO Specifications
Capacity	120GB	250GB	500GB	1TB	2TB
Controller	MGX			MEX	MHX
NAND	Samsung 32-layer 128Gbit TLC V-NAND
DRAM	256MB	512MB		1GB	2GB
Sequential Read	540MB/s	540MB/s	540MB/s	540MB/s	540MB/s
Sequential Write	520MB/s	520MB/s	520MB/s	520MB/s	520MB/s
4KB Random Read	94K IOPS	97K IOPS	98K IOPS	98K IOPS	98K IOPS
4KB Random Write	88K IOPS	88K IOPS	90K IOPS	90K IOPS	90K IOPS
DevSleep Power	2mW	2mW	2mW	4mW	5mW
Slumber Power	50mW				60mW
Active Power (Read/Write)	Max 3.7W / 4.4W				3.7W / 4.7W
Encryption	AES-256, TCG Opal 2.0, IEEE-1667 (eDrive)
Endurance	75TB		150TB
Warranty	Five years

Like the 2TB Pro, the EVO has similar performance characteristics with the 1TB model. Only power consumption is higher, but given the increase in NAND and DRAM capacities that was expected.

As the 32-layer TLC V-NAND die was 128Gbit to begin with, Samsung didn't need to develop a new higher capacity die to bring the capacity to 2TB. The EVO also uses eight 16-die packages with the only difference to Pro being TLC NAND, which is more economical to manufacture since storing three bits in one cell yields higher density than two. Out of the 2,048GiB of raw NAND, 2,000GB is user-accessible, which is 48GB less than in the 2TB 850 Pro, but the TurboWrite SLC cache eats a portion of NAND and TLC tends to require a bit more over-provisioning to keep the write amplification low for endurance reasons.

AnandTech 2015 SSD Test System
CPU	Intel Core i7-4770K running at 3.5GHz (Turbo & EIST enabled, C-states disabled)
Motherboard	ASUS Z97 Deluxe (BIOS 2205)
Chipset	Intel Z97
Chipset Drivers	Intel 10.0.24+ Intel RST 13.2.4.1000
Memory	Corsair Vengeance DDR3-1866 2x8GB (9-10-9-27 2T)
Graphics	Intel HD Graphics 4600
Graphics Drivers	15.33.8.64.3345
Desktop Resolution	1920 x 1080
OS	Windows 8.1 x64

• Thanks to Intel for the Core i7-4770K CPU
• Thanks to ASUS for the Z97 Deluxe motherboard
• Thanks to Corsair for the Vengeance 16GB DDR3-1866 DRAM kit, RM750 power supply, Hydro H60 CPU cooler and Carbide 330R case

Performance Consistency

We've been looking at performance consistency since the Intel SSD DC S3700 review in late 2012 and it has become one of the cornerstones of our SSD reviews. Back in the days many SSD vendors were only focusing on high peak performance, which unfortunately came at the cost of sustained performance. In other words, the drives would push high IOPS in certain synthetic scenarios to provide nice marketing numbers, but as soon as you pushed the drive for more than a few minutes you could easily run into hiccups caused by poor performance consistency. 

Once we started exploring IO consistency, nearly all SSD manufacturers made a move to improve consistency and for the 2015 suite, I haven't made any significant changes to the methodology we use to test IO consistency. The biggest change is the move from VDBench to Iometer 1.1.0 as the benchmarking software and I've also extended the test from 2000 seconds to a full hour to ensure that all drives hit steady-state during the test.

For better readability, I now provide bar graphs with the first one being an average IOPS of the last 400 seconds and the second graph displaying the IOPS divided by standard deviation during the same period. Average IOPS provides a quick look into overall performance, but it can easily hide bad consistency, so looking at standard deviation is necessary for a complete look into consistency.

I'm still providing the same scatter graphs too, of course. However, I decided to dump the logarithmic graphs and go linear-only since logarithmic graphs aren't as accurate and can be hard to interpret for those who aren't familiar with them. I provide two graphs: one that includes the whole duration of the test and another that focuses on the last 400 seconds of the test to get a better scope into steady-state performance. These results are for all drives 240GB and up.

In steady-state 4KB random write performance the EVO is actually slightly faster than the Pro, but given that the EVO employs more over-provisioning (12% vs 7%), it's not out of the ordinary. The 2TB EVO performs slightly lower than the 1TB model, so it seems that despite the upgraded DRAM controller the controller may not be ideal for more than 1TB of NAND (internal SRAM caches and the like are the same as in the MEX controller). Nevertheless, the difference isn't substantial and in any case the Pro and EVO both boast excellent steady-state performance.

Both 2TB drives also have great consistency, although the 2TB Pro can't challenge the 512GB Pro that clearly leads the consistency graph. Given the same amount of raw processing power, managing less NAND is obviously easier because the more NAND there is, the more garbage collection calculations the controller has to process, which results in increased variation in performance.

Default	Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB
25% Over-Provisioning	Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 240GBADATA XPG SX930 480GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCorsair Neutron XT 480GBCrucial MX100 512GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

The behavior in steady-state is similar to other 850 Pro and EVO drives, which is hardly surprising given the underlying firmware similarities. One area to note, though, is the increased performance variation with additional over-provisioning (OP), whereas especially the 512GB Pro presents very consistent performance with 25% OP. In any case, performance with additional OP is class-leading in both Pro and EVO.

Default	Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB
25% Over-Provisioning	Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 240GBADATA XPG SX930 480GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCorsair Neutron XT 480GBCrucial MX100 512GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

AnandTech Storage Bench - The Destroyer

The Destroyer has been an essential part of our SSD test suite for nearly two years now. It was crafted to provide a benchmark for very IO intensive workloads, which is where you most often notice the difference between drives. It's not necessarily the most relevant test to an average user, but for anyone with a heavier IO workload The Destroyer should do a good job at characterizing performance. For full details of this test, please refer to this article.

The 2TB Pro appears to be marginally slower than the 1TB model, but honestly we are talking about a ~5% difference. As I mentioned on the previous page, managing more NAND requires more controller resources and since the MHX is fundamentally an MEX with a beefier DRAM controller, a tiny performance hit is normal and despite that the 2TB Pro and EVO are still the fastest SATA drives on the market.

There's an increase in >10ms IOs, which I suspect is again due to the higher performance variation caused by the additional management resources required by the extra NAND.

The 2TB Pro turns out to have better power efficiency than its 512GB sibling. Normally smaller drives are more efficient due to having less NAND drawing power, but it may very well be that Samsung has moved to a more power efficient process node for the MHX controller, which would explain the lower power consumption.

AnandTech Storage Bench - Heavy

While The Destroyer focuses on sustained and worst-case performance by hammering the drive with nearly 1TB worth of writes, the Heavy trace provides a more typical enthusiast and power user workload. By writing less to the drive, the Heavy trace doesn't drive the SSD into steady-state and thus the trace gives us a good idea of peak performance combined with some basic garbage collection routines. For full details of the test, please refer to the this article.

In our Heavy trace, the 1TB and 2TB Pros are practically on par. The 2TB EVO enjoys a slight advantage over the 1TB model, which is likely due to the larger SLC cache being able to cache more writes.

The 2TB models are again more power efficient than their 1TB counterparts. It's a welcome improvement since especially the 850 EVO isn't the most power efficient drive for laptops (at least when compared against the BX100).

AnandTech Storage Bench - Light

The Light trace is designed to be an accurate illustration of basic usage. It's basically a subset of the Heavy trace, but we've left out some workloads to reduce the writes and make it more read intensive in general. Please refer to this article for full details of the test.

The situation in our Light workload is similar to the Heavy one where the performance difference between 1TB and 2TB models is essentially negligible.

One interesting aspect to note is that the 2TB EVO had zero IOs with latency over 10ms. I had to put 0.01 in the graph because our software wouldn't display zero result at all. The Light trace has so few writes that it actually fits in the SLC cache, explaining why the 2TB EVO has no high latency IOs. When running the test on a filled drive (i.e. can't take advantage of SLC cache), the EVO has equal portion of >10ms IOs as most of the other drives.

Power consumption is again lower than 1TB models and brings the EVO to the level of other drives.

Random Read Performance

For full details of how we conduct our Iometer tests, please refer to this article.

Random read performance is unchanged from the 1TB models, but as we already noticed in the Storage Bench tests the 2TB models are more power efficient.

Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ ARC 100 240GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

Despite having equal performance at low queue depths, the 2TB models don't performance as well at QD8 and QD16. It's a marginal difference, but it's an interesting observation that further speaks for the controller not being ideal for over 1TB of NAND.

Random Write Performance

Random write performance is also equivalent to 1TB Pro and EVO, but power consumption decreases, resulting in increased power efficiency.

Similarly, queue depth scaling is identical to smaller capacities.

Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ ARC 100 240GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

Sequential Read Performance

For full details of how we conduct our Iometer tests, please refer to this article.

Most modern SATA drives have more or less the same sequential read performance and the 2TB Pro and EVO are no exceptions. Samsung drives do consume quite a bit of power under sequential read operations, but fortunately the 2TB EVO shows efficiency gains over the 1TB model.

Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ ARC 100 240GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

Nothing special in the scaling graphs -- both the Pro and EVO reach their maximum at QD2.

Sequential Write Performance

Once again, the performance of 2TB models is equal to 1TB with the EVO having increased power efficiency.

Queue depth scaling is, unsurprisingly, similar to the smaller capacities.

Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ ARC 100 240GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

Mixed Random Read/Write Performance

For full details of how we conduct our Iometer tests, please refer to this article.

In mixed 4KB random performance the 2TB Pro shows rather significant gains over the 512GB model. I was always surprised how poorly the 850 Pro performed in this test, so it's good to see Samsung paying attention to this, especially since the performance increase comes with dramatically improved power efficiency.

Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ ARC 100 240GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

The 512GB Pro had performance and power issues once over half of the IOs were writes, but the 2TB model shows quite optimal performance scaling.

Mixed Sequential Read/Write Performance

In mixed sequential workload performance of both the 2TB Pro and EVO is further improved with the Pro topping the chart. The 2TB EVO is again more power efficient than the 1TB model, whereas the 2TB Pro consumes only a little more power than the 512GB model (this was expected because large sequential IOs utilize multiple dies and with 2TB having more NAND there are more dies drawing power).

The improvement has been in the critical 60/40 and 40/60 distributions. Quite a few drives have an infamous "bathtub" curve where performance severely degrades, but the 2TB Pro and EVO are fairly consistent though all distributions. It's great to see Samsung improving mixed performance because typically it has been an area that has been forgotten in client SSDs, but under real world workloads IOs tend consist of both reads and writes.

Samsung 850 Pro 2TBSamsung 850 EVO 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ ARC 100 240GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

Idle Power Consumption

Since we truncate idle times to 25µs in our Storage Bench traces, they don't give a fully accurate picture of real world power consumption as idle power consumption is not taken properly into account. Hence I'm still reporting idle power consumption as a separate benchmark because it's one of the most critical metrics when it comes evaluating an SSD for mobile use.

Unfortunately I still don't have a way to test DevSleep power consumption due to lack of platform support, but my testbed supports HIPM+DIPM power commands (also referred to as Slumber power), so the results give a rather accurate picture of real-world idle power consumption. 

Idle power consumption is increased by a rather large margin. With a beefier DRAM controller and more DRAM drawing power, I was expecting higher idle power draw, but not over twice the power. Still, the Pro and EVO are among the most power efficient drives under idle, making them good for mobile use.

ATTO - Transfer Size vs Performance

ATTO is a handy tool for quickly measuring performance across various transfer sizes and it's also freeware that can easily be run by the end-user.

Samsung 850 Pro 2TBADATA XPG SX930 120GBADATA XPG SX930 240GBADATA XPG SX930 480GBCorsair Neutron XT 480GBCrucial BX100 120GBCrucial BX100 250GBCrucial BX100 500GBCrucial BX100 1TBCrucial MX100 512GBCrucial MX200 250GBCrucial MX200 500GBCrucial MX200 1TBJMicron JMF670H 120GBJMicron JMF670H 240GBJMicron JMF670H 480GBOCZ Trion 100 240GBOCZ Trion 100 480GBOCZ Trion 100 960GBOCZ Vector 180 240GBOCZ Vector 180 480GBOCZ Vector 180 960GBSamsung 850 EVO M.2 120GBSamsung 850 EVO mSATA 250GBSamsung 850 EVO M.2 500GBSamsung 850 EVO mSATA 1TBSamsung 850 EVO 1TBSamsung SSD 850 Pro 512GBSanDisk Extreme Pro 480GBSanDisk Ultra II 240GBSMI 2256 Reference Design 500GB

 

AS-SSD Incompressible Sequential Performance

Similar to ATTO, AS-SSD is freeware as well and uses incompressible data for all of its transfers, making it a valuable tool when testing drives with built-in compression engines (e.g. SandForce).

Final Words

The 850 Pro and EVO are undoubtedly the best SATA 6Gbps SSDs on the market. The Pro has been holding the performance crown for the past year and it's starting to look like no SATA drive can dethrone it, whereas the EVO provides very competitive performance at a much more affordable price point. From a performance standpoint, the 2TB models leave the Pro and EVO lines unchanged as the performance matches with the 1TB models already on the market. That's hardly a surprise given that the 1TB models saturate the SATA 6Gbps interface and AHCI presents its own limitations, so the 2TB SKUs are solely a capacity bump. There are minor performance differences in steady-state 4KB random write and random read benchmarks that favor the 1TB models, but to be honest that's merely an architectural observation (the internal SRAM caches in the controller may need upgrading to extract better performance out of +1TB of NAND) because the impact on actual user performance is in the order of a few percent. 

I'm very glad to see improved power efficiency in the 2TB models. A part of that is explained by the move from LPDDR2 to LPDDR3, but it's also possible that the MHX is manufactured using a more power efficient process node. Depending on the benchmark the power savings can be anywhere from 5% to close to 20%, so it's not a marginal gain especially because higher capacity SSDs usually consume more power due to the additional NAND. The 850 EVO in particular wasn't very power efficient before, but the new 2TB is mostly on par with the 1TB-class drives we have tested. It's no challenger to the BX100 though, but TLC is inherently less power efficient and the SM2246EN controller is also less powerful by being a single-core design while the MHX consists of three processor cores. 

At $800, the 2TB 850 EVO is very reasonably priced. The average going price for a 1TB-class value SSD is about $350-$380 with an occasional sale bringing the price closer to $300, so the 2TB EVO carries a small premium, but at $0.40 per gigabyte it's not overpriced by any means. The $1000 2TB Pro on the other hand has a much tinier niche because unless you have a The Destroyer level workload there won't be any difference in performance. Even under such an intensive IO workload the Pro only has a ~10% advantage, but the Pro is overall a little (~5-10%) more power efficient, so if you need a 2TB SSD and value every extra minute of battery life high, the $200 premium might be justifiable. The Pro also carries twice the endurance (300TB vs 150TB) and warranty (10 vs 5 years), but I don't consider those two having much value given that 150TB already translates to 82GB a day for five years and in five years time a SATA 6Gbps drive will most likely be obsolete anyway.

Since the 850 Pro and EVO are the first 2TB client SSDs on the market so they face no competition. They receive a strong recommendation from us for those who need/want a 2TB SSD. Both have excellent performance like the 1TB models we had already tested and the increased power efficiency is a welcome addition for mobile users. Out of the two the EVO is better value for the vast majority, but the 2TB Pro is there for those who want the added endurance and the most impressive SATA SSD in the market.