Samsung 850 EVO And 850 Pro 2TB SSD Review

Introduction

A few days ago, we published a Tom's Hardware State of Solid State editorial that discussed what we will see from SSD vendors in the second half of 2015. That story has a lot of information in it, but only covers 50% of the market. Samsung owns most of the market, after all.

Samsung owns 50% of the solid-states storage market share. When it comes to client-oriented drives, that percentage increases, and in some countries goes as high as 80%. Samsung manufactures roughly 50% of the world's NAND memory supply, too. Not all of the flash goes into SSDs; much of it goes into cell phones, tablets, children's toys, SD cards and even automobiles.

Samsung doesn't just lead in production volume. It also leads in technology innovation as well. Recently, Samsung was responsible for delivering the first client three-bit-per cell-based SSD, along with the first 3D cell structure SSD in both MLC and TLC. Today, the company brings us the first widely available 2TB 2.5" client-focused drive.

Since the release of the first 1TB SSD, enthusiasts have looked to the next capacity point. It's always easy to demand a bigger, faster or better product. But when push comes to shove, those jumps only happen when there's financial impetus. I can ask for a Ferrari SUV that can comfortably hold eight passengers, but that doesn't mean Ferrari would make any money on it, or that I could afford such a monstrosity. Clearly, Samsung determined that the time was right for 2TB SSDs to become more commonplace.

Technical Specifications

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Although they aren't groundbreaking, the 2TB 850 Pro and EVO drives do add some excitement to both line-ups. For the most part, Samsung simply added twice as much NAND to get to 2TB. It also doubled the on-board cache and upgraded it to low-power DDR3 (LPDDR3) for the largest capacity size. The DDR3 runs at a higher clock speed and uses less power than the older DDR2. Both increases are offset by the larger table maps (speed) and more NAND dies (power).

A new controller was necessary to support twice as many CE paths to the 32-layer V-NAND flash. This does increase interleaving, and you will see the impact of this in the performance results, even if officially, Samsung specs the 850 Pro 2TB and 850 EVO 2TB for the same performance as its 1TB models.

The 2TB capacity point really favors the 850 EVO more than the Pro. You're going to see a huge price gap right off the bat, but there's more to the story than just a $200 difference. The Samsung 850 EVO 2TB uses TurboWrite technology, a layer of emulated SLC flash that acts as a buffer for data writes. With more flash on the drive, Samsung was able to increase the amount reserved for TurboWrite. We had to push the drive really hard to figure out where the cache ended and TLC write performance began. Outside of working with massive video files in a workstation environment, you'll probably never observe writes at TLC speeds. 

Both new products support Self-Encrypting Drive (SED) technology like existing models. We hope that many power users will take advantage of eDrive, Microsoft's Windows-based IEEE-1667 encryption technology, but TCG Opal is supported as well.

Samsung's documentation shows the 2TB models using slightly more power under different conditions than the 1TB versions. You may be tempted to interpret that as less notebook battery life, but in practice, that's not the case. The increased interleaving, as well as the larger TurboWrite area (850 EVO-only) yield more time away from a wall socket, actually. We'll go into more depth on this shortly.

Pricing, Warranty And Accessories

Samsung's 850 Pro 2TB (MZ-7KE2T0BW) is accompanied by an MSRP of $999.99, while the 850 EVO 2TB (MZ-75E20B/AM) should sell for $799.99. Both are available in drive-only packages devoid of anything except the SSD itself. You can download Samsung's Data Migration utility for cloning and Magician for diagnosis and administration of RAPID Mode (DRAM cache) at Samsung's support website. The software package is one of the best in the industry and shouldn't be overlooked.

The standard 850 Pro 10-year warranty and 850 EVO five-year warranty apply to the 2TB SSDs. Both guarantees are class-leading compared to competing storage products. Just bear in mind that the coverage is capped by endurance ratings, though this is another area where Samsung leads or is near the top.

A Closer Look

In this section, you'll find the 850 Pro on the left side and the 850 EVO on the right. For most of the single-drive pictures, we use the 850 Pro, though Samsung's 850 EVO ships with the same package contents.

In the box, there's an installation guide and warranty statement, both in paper form. We also find a small sticker sheet for those who enjoy advertising their hardware elsewhere. The drive is secured in a plastic form-fit case.

Both SSDs employ a 2.5", 7mm form factor, so they'll easily fit in notebooks that require the thinner z-height.

The PSID is clearly printed on the back of each drive, allowing you to manage the SED features either on the host or remotely.

Inside, we observe a new PCB design that allows Samsung to fit eight flash memory packages. To get to 2TB, the company simply doubles the number of packages and dies compared to the 1TB models. Samsung still doesn't need to use the full area inside of its enclosure.

The 850 Pro and 850 EVO 2TB drives look the same inside.

Both models use a new Samsung MHX controller and Samsung LPDDR3 DRAM. We suspect that Samsung needed the updated logic to address more NAND packages. This would also strengthen our hypothesis that Samsung has a modular controller design that can be updated in stages according to application.

Samsung still leads the industry in flash technology. On the left, we see MLC 3D V-NAND; on the right is TLC 3D V-NAND. We don't expect 3D cell structure-based memory from IMFT or Flash Forward in retail products until 2016.

Data Type Comparison & TLC Sequential Write Speed

Samsung's architecture doesn't discriminate between compressible and incompressible data. Both data types move to and from the flash at full speed. We rarely mention this unless one data type enjoys higher performance than the other. But we want to bring it up this time because we expect another 2TB SSD to hit the market soon, which will be biased to one data type. 

In our Computex coverage of TLC-based products, we talked about the need to hide TLC's low write speeds. All of the products we've tested with triple-level-cell flash utilize some form of emulated SLC write cache that yields better performance in short bursts, but quickly falls back to native TLC write speeds once the buffer fills. In some cases, that means sequential write performance as low as 125 MB/s.

Most of the time you'll never see rates that low since the cache is deliberately large enough to soak up the writes. That changes when transferring large files like big movies, though.

Samsung does an excellent job masking the native TLC performance with its 850 EVO. We had to really work to build a write test that'd shed more light on the sequential write performance of TLC. The 850 EVO 2TB has so much emulated SLC from TurboWrite that even a 42GB Blu-ray image transfer doesn't slow down.

Sequential Read

To read about our storage tests in-depth, please check out How We Test HDDs And SSDs. Four-corner testing is covered on page six.

Both of the drives we're reviewing deliver nearly identical sequential write performance. The two even overlap in our line chart, joining a number of comparison products that flirt with the upper limit of SATA 6Gb/s.

Sequential Write

The only drives faster than Samsung's 850 Pro and EVO 2TB in sequential writes are the 850 Pro and EVO 1TB. All four SSDs overlap each other on the line chart, delivering identical performance as the queue depth increases. Other high-capacity products also deliver impressive results. But the new 2TB models from Samsung are in a class unto themselves.

Random Read

Samsung's 2TB drives benefit from increased parallelism, moving them to the top of the performance charts at low queue depths in our random read test. These are the first SATA-based samples we've seen break 11,000 IOPS without the aid of DRAM cache. At higher queue depths, the 2TB models trail the 1TB drives slightly.

Random Write

The new 2TB drives fall in the middle of the pack when it comes to random writes. At high queue depths, we see how the 850 EVO 2TB delivers better random write performance than the 1TB model.

This test doesn't take the drives down to enterprise-class steady state, but it does involve heavy preconditioning that doesn't doesn't affect the 2TB model like it does Samsung's 1TB 850 EVO.

Sequential 80% Read Mixed Workload

Our mixed workload testing is described in detail here, and our steady state tests are described here.


There aren't many tests where performance varies between Samsung's 2TB SSDs. Mixed workloads is an exception. In this test, lower-latency MLC flash proves superior to TLC. The 850 Pro 2TB is also generally better than its competition, though several other drives do perform similarly at some queue depths.

Random 80% Read Mixed Workload

In our previous tests with random data, the 850 Pro 1TB delivered slightly more performance than the 2TB model. Now, in the random 80% read mixed workload benchmark, Samsung's 1TB Pro is still a bit faster. The 2TB EVO does outperform the 1TB version, but only by a small margin. 

Sequential Steady State

In steady state, the 850 Pro delivers higher performance than the 850 EVO, while the 850 EVO 2TB serves up similar results we often see from MLC-based drives from other vendors. The EVO 2TB also outshines the EVO 1TB by a large margin at both ends of the scale, as well as every mixed workload in between.

Random Write Steady State

In the preconditioning stage, there are too many drives to really distinguish one product from another. Since we've borrowed this test from the enterprise SSD world, we stick to the enterprise standard showing the preconditioning curve, even though it's mostly meaningless to desktop computing. The problem with showing so many consumer SSDs is that most weren't designed to deliver the steady random write performance an enterprise drive can. Our results are all over the place as a result.

And then there are the new Samsung 850 2TB drives that manage to keep the deviation small, while maintaining a consistent 10,000-ish random write IOPS. The 2TB drives outperform the 850 Pro 1TB. But the real shocker is that the 850 EVO 2TB even outperforms the 850 Pro 2TB. Samsung's TurboWrite technology, which gives the EVO 2TB SSD an emulated SLC layer, is now too good.

PCMark 8 Real-World Software Performance

For details on our real-world software performance testing, please click here.

In many of these tests, all four Samsung 850 products come out at the top of the performance charts. Notably, though, the 850 Pro 2TB has an issue with the Photoshop Heavy metric that we never managed to sort out; it proved to be an issue in all three passes and in the three test runs we made.

Total Storage Bandwidth

With all of the results combined, we can look at performance in terms of throughput rather than time. The tide starts to turn when we dive into light real-world workloads. The 850 EVO's SLC cache accelerates the 2TB model past both of the 850 Pros. I wouldn't think this could be true without seeing it firsthand, but Samsung managed to make a TLC-based SSD better than its MLC-based counterpart. Of course, that won't hold true in all workloads. However, the 2TB 850 EVO masks TLC's weaker performance so well that we actually prefer it.

PCMark 8 Advanced Workload Performance

To learn how we test advanced workload performance, please click here.

We were surprised to see the 850 EVO 2TB outperform the 850 Pro 2TB in this series of tests. Unlike the previous benchmark results from PCMark 8, these run under more demanding conditions, with less time between each metric. They aren't enterprise-oriented, but come close to that level of load.

Normally we see the SanDisk Extreme Pro 1TB dominate this discipline, with the 850 Pro 1TB close behind. Under the lighter workloads, we expect the 850 Pro 2TB to outperform the smaller 1TB model. However, it just couldn't recover fast enough to climb back.

We would normally suspect a TRIM issue. But the 850 EVO recovered well and led the light workload portion of the test.

Latency Test

The latency numbers show us where the 850 Pro 2TB falls short and where the 850 EVO 2TB turns into a beast. Under heavy load, Samsung's 850 Pro 2TB took nearly twice as long to complete the tests as the 850 Pro 1TB. When the drives are given time to recover, the 850 Pro 2TB fails to clean the NAND or direct the data writes to clean flash. This is something Samsung will need to look into and fix in a future firmware update.

The 850 EVO 2TB performs better than we expected under demanding conditions, and then brings the service times down to class-leading levels when it's given time to recover.

Notebook Battery Life

For more information on how we test notebook battery life, click here.


The momentum continues in the 850 EVO's favor. Earlier, we suggested that the 2TB model would serve up more notebook battery life than the 850 Pro, even though the specifications suggest that Samsung's Pro uses less power. I love it when the results turn out this way because they throw everyone off.

When companies measure SSD power they do it looking at all four corners of performance. When the test is over, the meter stops and the results are recorded. SSDs don't actually stop working when the workload ends, though. If we write a 5GB file, the data moves and the system resumes normal operation (to our eyes). The SSD doesn't see it that way. Rather, after the transfer, the controller takes over and moves information around, cleaning flash cells and preparing the emulated SLC for its next task.

In the measurement of of notebook battery life, it isn't just about the amount of power consumed during the initial workload, but also the trailing end power use as well. The faster a drive can finish shuffling data, the less power is used overall.


The 850 EVO 2TB's SLC is so good that it allows the drive to deliver the best notebook performance in a power-restricted environment we've seen. In this measurement, each point represents a large change in user experience. We normally only see small variations since the CPU, GPU and system buses are running in a low-power mode to conserve energy. Given that the only difference between these configurations is the SSD, Samsung's 850 EVO proves that SLC is more efficient than MLC (and every other competing drive).

Final Thoughts

Even without any performance improvements, Samsung gets recognition for introducing the first viable 2TB SSDs. Not everyone needs a drive with this much capacity, and the price tags will sort out the true believers from the tire-kickers. Desktop enthusiasts always have the option to add 4TB+ hard drives to their machines. But mobile users are more space-constrained; they don't have that flexibility. Cloud storage was supposed to be the mobile storage savior; however, it seems like the only ones excited about that are ISP executives.

In my experience, there is no doubt about the need for the products Samsung is introducing. As I type, I'm also trying to move several hundred gigabytes of data from my notebook to keep its free space indicator out of the red. This is a common problem that is slowly being eliminated by larger, lower-priced flash-based devices. Samsung's new 2TB options will further reduce the time between notebook data flushes to NAS or other backup appliances.

We spent a lot of time exploring the 850 Pro 2TB performance abnormality we found, but not enough to isolate the problem. This is a bad time for Samsung to have firmware issues. Some users are still reporting slow-downs on the 840 EVO, even after the company attempted multiple fixes. The 840 EVO is the best-selling client SSD of all time. But the transition to three-bit-per-cell flash may have come too soon or without powerful-enough ECC to tame it.

The new 850 EVO 2TB, on the other hand, could be one of the best client SSDs ever released. The smaller EVO models managed to keep TLC performance at MLC levels. However, the largest capacity point moves the 850 EVO into SanDisk Extreme Pro territory. It's now a part of the top performance tier thanks to even larger TurboWrite emulated SLC memory that can even keep large transfers in single-bit-per-cell latency levels.

The largest drawback to both new Samsung 2TB SSDs is their price. Without competition, Samsung can ask almost as much as it wants. The 850 Pro 2TB runs $999. The 850 EVO 2TB is almost a value in comparison at $799. The comments section is going to dislike this, but once you look at the EVO 2TB for all it offers, that value story comes into greater focus. Samsung could have placed a premium on the 850 EVO 2TB, but the MSRP is in line with current pricing, twice what you'd pay for the 1TB EVO.

Samsung 850 Pro 2TB

Samsung 850 Pro 2TB

Pros

• The first widely available workstation-class 2TB SSD.

Cons

• We're disappointed to see a programming/firmware-related issue on release, particularly after the 840 EVO problems.

Verdict

The price is an obvious issue, but it's one we expected. It's important to be realistic about your workload. The 850 EVO 2TB really closed the gap, so if you don't plan to hit steady state levels, there's no use in splurging on the Pro model.

Review

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Samsung 850 EVO 2TB

Samsung 850 EVO (2TB)

Pros

• Exceptional performance and a discounted price compared to the 850 Pro 2TB.

Cons

• At nearly $800, the 850 Evo 2TB isn't cheap, though it does deliver a fantastic user experience.

Verdict

Where do we start? This is the best client SSD we've seen in 2015. The 850 Evo 2TB even causes us to second-guess the new NVMe products that can't hold the same amount of data. Users will have to choose performance or capacity, but in many cases high performance with a lot of capacity is good enough.

Review

$699.99Amazon

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Chris Ramseyer is a Contributing Editor for Tom's Hardware, covering Storage. Follow him on Twitter and on Facebook.

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