Over the last three years, Samsung has become one of the most dominant players in the SSD industry. Samsung's strategy has been tight vertical integration ever since the beginning, which gives Samsung the ability to be in the forefront of new technologies. That is a massive advantage because ultimately all the parts need to be designed and optimized to work properly together. The first fruit of Samsung's vertical integration was the SSD 840, which was the first mass produced SSD to utilize TLC NAND and gave Samsung a substantial cost advantage. Even today, the SSD 840 and its successor, the 840 EVO, are still the only TLC NAND based SSDs shipping in high volume. Now, two years later, Samsung is doing it again with the introduction of the SSD 850 Pro, the world's first consumer SSD with 3D NAND.

For years it has been known that the scalability of traditional NAND is coming to an end. Every die shrink has been more difficult than the previous as the endurance and performance have decreased with every node, making it less and less efficient to scale the size down. Scaling below 20nm was seemed as a major obstacle but the industry was able to cross that with some clever innovations in the NAND design. However, the magic hat is now running out of tricks and a more signficant change to the NAND design is required to keep scaling the cost. 

The present solution to the scalability problem is 3D NAND, or V-NAND as Samsung calls it. Traditionally NAND and other semiconductors are scaled horizontally along the X and Y axes but due to the laws of physics, there is a limit of how small the transistors can be made. To solve the problem, 3D NAND introduces a Z-axis i.e. a vertical dimension. Instead of cramming transistors horizontally closer and closer to each other, 3D NAND stacks layers of transistors on top of each other. I will be going through the structure and characteristics of 3D NAND in detail over the next few pages.

By stacking transistors (i.e. cells when speaking about NAND) vertically, Samsung is able to relax the process node back to a much more convenient 40nm. When there are 32 cells on top of each other, it is obvious that there is no need for a 10nm-class node because the stacking increases the density, allowing production costs to scale lower. As we have seen with the history of NAND die shrinks, a higher process node provides more endurance and higher performance, which is what the 850 Pro and V-NAND is all about.

Fundamentally the only change in the 850 Pro is the switch to V-NAND. The interface is still SATA 6Gbps and the controller is the same triple-core MEX from the 840 EVO, although I am still waiting to hear back from Samsung whether the clock speed is the same 400MHz. The firmware, on the other hand, has gone through a massive overhaul to adopt the characteristics of V-NAND. With shorter read, program and erase latencies and higher endurance, the firmware needs to be properly optimized or otherwise the full benefits of V-NAND cannot be utilized. 

I bet many of you would have liked to see the 850 Pro move to the PCIe interface but I understand Samsung's decision to hold off with PCIe for a little while longer. The market for aftermarket PCIe SSDs is still relatively small as the PC industry is figuring out how to adopt the new interface, so for the time being Samsung is fine with watching from the side. The XP941 is and will continue to be available to the PC OEMs but for now Samsung will be keeping it that way. From what I have heard, Samsung could bring the XP941 to the retail market rather quickly if needed but Samsung has always been more interested in the high volume mainstream market instead of playing in the niches. 

Samsung SSD 850 Pro Specifications
Capacity 128GB 256GB 512GB 1TB
Controller Samsung MEX
NAND Samsung 2nd Gen 86Gbit 40nm MLC V-NAND
DRAM (LPDDR2) 256MB 512MB 512MB 1GB
Sequential Read 550MB/s 550MB/s 550MB/s 550MB/s
Sequential Write 470MB/s 520MB/s 520MB/s 520MB/s
4KB Random Read 100K IOPS 100K IOPS 100K IOPS 100K IOPS
4KB Random Write 90K IOPS 90K IOPS 90K IOPS 90K IOPS
Power 2mW (DevSLP) / 3.3W (read) / 3.0W (write)
Encryption AES-256, TCG Opal 2.0 & IEEE-1667 (eDrive supported)
Endurance 150TB
Warranty 10 years
Availability July 21st

The performance figures in the table above give us the first glimpse of what V-NAND is capable of. Typically modern 128GB SSDs are only good for about 300MB/s but the 850 Pro is very close to saturating the SATA 6Gbps bus even at the smallest capacity. This is due to the much lower program times of V-NAND because write performance has been bound by NAND performance for quite some time now. 

Endurance Comparison of High-End SSDs
Samsung SSD 850 Pro Intel SSD 730 SanDisk Extreme Pro OCZ Vector 150
150TB 91TB (240GB)
128TB (480GB)
80TB 91TB

The other major improvement from V-NAND is the endurance. All capacities, including the smallest 128GB, are rated at 150TB, which is noticeably higher than what any other consumer-grade SSD offers. Moreover, Samsung told me that the endurance figure is mainly meant to separate the 850 Pro from the enterprise drives to guide enterprise clients to the more appropriate (and expensive) drives as the 850 Pro does not have power loss protection or end-to-end data protection for example. However, I was told that the warranty is not automatically denied if 150TB is reached under a client workload. In fact, Samsung said that they have a 128GB 850 Pro in their internal testing with over eight petabytes (that is 8,000TB) of writes and the drive still keeps going, so I tip my hat to the person who is able to wear out an 850 Pro in a client environment during my lifetime.

Another interesting aspect of V-NAND is its odd capacity per die. Traditionally NAND capacies have come in powers of two, such as 64Gbit and 128Gbit, but with V-NAND Samsung is putting an end to that trend. The second generation 32-layer V-NAND comes in at 86Gbit or 10.75GB if you prefer the gigabyte form. I will be covering the reason behind that in more detail when we look at V-NAND more closely in the next few pages but as far as I know there has never been a strict rule as to why the capacities have scaled in powers of two. I believe it is just a relic from the old days that has stayed in the memory industry because deep down binary is based on powers of two but the abnormal die capacity should have no effect on the operation of the NAND or the SSD as long as everything is optimized for it. 

NAND Configurations
  128GB 256GB 512GB 1TB
# of NAND Packages 4 (?) 4 8 (?) 8
Package Configurations 2 x 4 x 86Gbit
2 x 2 x 86Gbit
2 x 8 x 86Gbit
2 x 4 x 86Gbit
4 x 8 x 86Gbit
4 x 4 x 86Gbit
4 x 16 x 86Gbit
4 x 8 x 86Gbit
Raw NAND Capacity 129GiB 258GiB 516GiB 1032GiB
Over-Provisioning 7.6% 7.6% 7.6% 7.6%

Due to the odd die capacity, the die configurations are also quite unusual. I found two different capacity packages inside my review samples and with Samsung’s NAND part decoder I was able to figure out the die configurations for each capacity. Unfortunately, Samsung did not send us the 512GB model and I could not get the 128GB model open as Samsung uses pentalobe Torx screws and I managed to wear out the screw while trying to open it with an inappropriate screw driver (it worked for the other models, though), so thus there are question marks at those capacities in the table. However, this should not impact the raw NAND capacities as long as all capacities follow the same 7.6% over-provisioning trend but the package configurations may be different. I will provide an update once I receive a confirmation from Samsung regarding the exact configurations for each capacity. 

The 850 Pro also switches to smaller PCB designs. The PCB in the 1TB model populates around two thirds of the area of the chassis, while the 256GB PCB comes in at even smaller size. The reason for the different PCB sizes is the amount of NAND packages as the 256GB only has four, whereas to achieve the capacity of 1TB eight NAND packages are required.

Why We Need 3D NAND
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  • GTVic - Tuesday, July 1, 2014 - link

    Wondering if the 3D V-NAND has an effect on heat produced by each chip?
  • Laststop311 - Wednesday, July 2, 2014 - link

    If only this drive would of been a pci-e 3.0 x4 interface with nvme. We would of finally had a worthy upgrade. Yes it's performance is better than the 840 evo but you can get the 840 evo 1tb for 400 dollars even less if you catch it on sale. So you can get 2x 1tb 840 evo for almost the same price as 1 850 pro. If you compare an 840 evo with 25% OP to a regular 7% on the 850 the 840 evo looks just as good so 2x 825GB drives with 25% OP on each drive costs you 750-800 depending on the deal you get vs 700 for 1000GB. I would rather pay 800 for 1650GB than 700 for 1000GB with performance being nearly identical. I get an extra 650GB (which at 50 cents per GB is another 325 dollars worth of ssd) and tons of over provisioning to give the drive equal or better performance for only 100 dollars more (possibly less as the 840 evo has often sales)

    Sorry Samsung but 2x 1tb 840 evos with 25% provisioning gives me better or equal performance and a whole 650GB of extra storage for only 100 dollars more. At 50 cents per GB you get 325 dollars worth of more storage capacity for only 100 dollars more and thats with the 25% over provisioning which basically negates the performance increase of the new drives.

    The only way samsung could of made this drive worth that money is if they had the drive on a pci-e 3.0 x4 interface with nvme instructions. I'm sure there will be tons of idiots who just buy it cause it's the latest drive. But if you use your brain you can see the 840 evo is still the best SATA drive when the cost/performance ratio is taken into account. 2x 1tb evo's in 25% OP mode gives you 1650GB and costs u 100 dollars extra or less and gives you the same performance or even better compared to 7% 850 pro 1000GB especially when raid 0 is taken into account. I'll take 1650GB over 1000GB if it's only 100 more and performance is equal or better easy choice.
  • Laststop311 - Wednesday, July 2, 2014 - link

    Since samsung is stacking vertically now what they should of done is made a super huge 2tb drive to differentiate themselves from all these other drives. A 2tb drive for 1400 is a little more acceptable than 1tb for 700 simply because it's the only single drive with 2TB capacity.

    I can see great things happening with vertical stacked nand tho. When this process matures we should be seeing nand drives surpass spinning hard drives in capacity. When samsung has those 1tbit dies its planning for 2017 we should be able to have 8-12TB SSD's
  • althaz - Wednesday, July 2, 2014 - link

    It's a new product and it's priced highly. Eager early adopters who want to move on to the latest and greatest will buy now, value-concious people will buy the 840s. Inventory of the 840s will get eaten up and the 850s will drop in price.

    This is what happens whenever any product is released, basically ever.
  • asmian - Wednesday, July 2, 2014 - link

    Sorry, but neither this nor the EVO will get my money. Performance is all very well, even if only a tiny handful of users with extremely niche workloads will ever notice any difference, but all this extra reliability at a price premium means NOTHING without simple power loss protection. Restricting something so basic to "Enterprise" class products is the real gouging here by Samsung, not the price.

    If Crucial can provide that protection on the CHEAPEST drives in their class (M500/M550 and IIRC MX100 too) with performance that is not gimped as a balance, then there is no excuse for Samsung not to. This should be a no-compromise baseline for all SSDs going forward, and Anandtech should push hard for that - users should as well, by voting with their wallets and refusing to buy drives, however fast and powerful, that do not provide power loss protection as a basic feature.
  • bsd228 - Wednesday, July 2, 2014 - link

    Though I agree it is a highly useful feature, it is far less significant to those of us using a good UPS. So I can't agree that it's a no compromise feature.
  • romrunning - Wednesday, July 2, 2014 - link

    What you aren't taking into account is the fact that the 850 Pro has MUCH higher endurance, and it's also more consistent. Those two items bring it more into the Intel DC 3500/3700 series type of class. It's not just a sheer performance comparison.

    ...and if you thing the 850 Pro is expensive, price out the larger Intel DC S3700 drives.
  • FunBunny2 - Wednesday, July 2, 2014 - link

    "Real" Enterprise SSDs don't even have an MSRP. You negotiate with the vendor, and hope for the best. Now that Texas Memory is in IBM, and Fusion-io in SanDisk, with Violin likely to go somewhere. The conundrum is V.NAND's impact on flattening the curve between Enterprise and Commodity/Retail. At one time, a mainframe had bespoke 14" behemoth hard drive subsystems (in the case of IBM, run by the equivalent of a PDP-x). In due time, binned commodity 3.5" drives are now used.

    Samsung could well be the driving force to regularize solid state storage. The remaining issue is whether the file system hand waving will be dumped in favor of direct NVM persistence? Samsung, or whoever, likely couldn't care less.
  • romrunning - Wednesday, July 2, 2014 - link

    It's been enjoyable to see a lot of "new" flash memory storage vendors pop-up. More competition is always good in that enterprise space.

    I've been looking forward to having more SSDs options available to servers at much better pricing. Solid storage advances have a trickle-down effect. If I can put an array of these Samsung 850 Pros into a server and achieve near "enterprise" performance, then that forces Dell/HP/etc. to drop their own SSD pricing.
  • watersb - Wednesday, July 2, 2014 - link

    Fantastic detail of 3D NAND design and why it matters. Thanks very much!

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