The next step for 3D V-NAND
2014 was an interesting year for SSDs. Adoption of SSDs has continue to rise thanks to falling prices; we also saw some players exit the market due to intensifying competition; and Samsung became the first to commercialize 3D V-NAND.
The SSD 850 Evo is Samsung's mainstream 3D V-NAND SSD and stores 3 bits of data per cell.
As detailed in our review of the Samsung SSD 850 Pro, 3D V-NAND is kind of a big deal as it addresses the shortcomings of current NAND lithography. We won’t go into detail here as we already discussed this quite extensively earlier, but to put it very briefly, 3D V-NAND stacks memory cells on top of each other in order to overcome the problem of squeezing cells closer and closer together. It’s an elegant and advantageous solution. Not only does this mean more cells can now be squeezed into a fixed area, stacking cells also improves performance, endurance and power efficiency. As a result, not only was the SSD 850 Pro the fastest drive we have ever tested, it was also one of the few drives to offer a whopping 10-year long warranty.
To say that the SSD 850 Pro was a great success would not be an overstatement, but the SSD 850 Pro was clearly a drive designed and priced for enthusiasts, and Samsung is keen to expand is 3D V-NAND offerings to other segments of the market, hence the SSD 850 Evo that we see here. Don’t be fooled into thinking that the SSD 850 Evo is just a watered down version of the SSD 850 Pro. This drive actually uses a lot of new components, which we will go into detail now.
To begin, while the early SSD 850 Pro used 32-layer 3D MLC V-NAND, the new SSD 850 Evo uses Samsung’s newest 32-layer 3D TLC V-NAND. We wrote about TLC NAND in great detail during our review of the SSD 840 Evo, but again to be put it briefly, TLC NAND increases memory density but at the cost of performance and endurance. However, given the benefits of the 3D architecture of 3D V-NAND, it is possible that the disadvantages of TLC NAND could be nullified, resulting in a faster mainstream SSD.
On top we have the older SSD 840 Evo and below lies the newer SSD 850 Evo. Samsung seems to have swap color schemes for the drives.
And thanks to this new 32-layer TLC 3D V-NAND, Samsung is also able to build higher capacity drives. And although we heard that a 2TB drive is actually possible, 1TB is unfortunately still the maximum that Samsung offers right now as Samsung believes that a 2TB drive would be priced much too high to be attractive to users.
Diving deeper, the density of this new TLC 3D V-NAND is 128Gbit, comparable to the latest MLC NAND from competitors such as Micron and also Samsung's old 19nm TLC NAND used in the SSD 840 Evo. In case you are wondering, the MLC 3D V-NAND used in the SSD 850 Pro has a memory density of 86Gbit. And because this new TLC 3D V-NAND is manufactured on a 40nm process node, Samsung has been able to increase the endurance of its new drive by a factor of about two. Typically speaking, TLC NAND drives enjoy roughly 1000 or so P/E cycles (program-erase), whereas Samsung's new TLC 3D V-NAND brings that figure to around 2000, which is comparable to most MLC NAND drives.
The Samsung SSD 850 Evo also has a new controller, dubbed simply as the MGX. This is a lower power dual-core controller that is used in the 120GB, 250GB and 500GB variants of the SSD 850 Evo. The 1TB variant employs the MEX controller, the same used in the SSD 850 Pro. The interface is still SATA 6Gbps, though it surely won't be long before we start seeing PCIe and M.2. variants of these drives.
Similar to the old SSD 840 Evo, the SSD 850 Evo also features TurboWrite and RAPID mode technologies. TurboWrite dedicates a small portion of its TLC NAND to work as an SLC write buffer, which is similar to SanDisk’s nCache technology. This helps boost its write performance to make up for the shortcoming of TLC NAND, which typically suffers from inferior write performance. RAPID mode, on the other hand, is a caching technology that was introduced in the middle of last year to boost random I/O performance with smaller size data at low queue depths. Essentially, it makes use of unallocated system memory and spare CPU cycles to cache data and boost performance. We investigated Samsung's RAPID mode technology and found it to work very well.
Samsung's Magician utility is easy to use and helps monitor the status and health of your drive.
Finally, like all Samsung SSDs, the SSD 850 Evo can be managed using Samsung's excellent Magician utility. The utility lets you check your drive's health status, update firmware, security settings and also enable or disable RAPID mode.
Test Setup
The Samsung SSD 850 Evo will be tested on our dedicated storage testbed:
- Intel Core i5-2500K (3.3GHz)
- ASUS P8Z77 Pro Thunderbolt (Intel Z77 chipset)
- 2 x 2GB DDR3-1600 memory
- MSI GeForce 8600 GTS
- Windows 7
Our revised benchmark ditches older benchmarks such as HD Tune and also includes an all new timing test to better evaluate the drive’s real world performance. The list of benchmarks used are as follows:
- AS-SSD benchmark 1.7.4739
- CrystalDiskMark 3.0.1
- PCMark 7 (Storage suite)
- Iometer (version 2006.07.27)
- Timing Tests (Cold start, Reboot, Apps Launching)
It will be interesting to see how the new SSD 850 Evo matches up against its predecessor, the SSD 840 Evo, and also Samsung’s flagship SSD 850 Pro. We also included results from comparable mainstream drives such as the Crucial MX100 and the Crucial M550.
Here is the list of drives tested:
- Samsung SSD 850 Evo
- Samsung SSD 840 Evo
- Samsung SSD 850 Pro
- Samsung SSD 840 Pro
- Crucial MX100
- Crucial M550
- Plextor M6 Pro
Timing tests
Recently added to our evaluation of SSDs is how they perform in real-world everyday situations, namely booting up from a cold start, reboot and launching applications. As for the applications used, we made the drives launch 11 applications from the Adobe CS6 suite of utilities simultaneously; they include resource-intensive applications such as Photoshop, InDesign, Dreamweaver, and Premiere Pro, amongst others. As a point of reference, a 7200rpm mechanical hard disk would take over 5 minutes to open all the applications.
The old Samsung SSD 840 Evo was not the quickest drive in our timing tests, so it is good that the new Samsung SSD 850 Evo improves on the timings recorded by its predecessors quite significantly. The time it took to boot from a cold start was reduced by a significant 1.7 seconds. Subsequently, the SSD 850 Evo could also reboot 1.4 seconds quicker. The SSD 850 Evo’s timings are now more comparable to the Crucial MX100 and M550, its keenest rivals in this segment. The SSD 850 Pro and even the older SSD 840 Pro are still the fastest drives in this test.
PCMark 7 results
PCMark 7 is a benchmarking suite from FutureMark that evaluates the performance of Windows 7 machines. It tests a wide range workloads and aspects of the system ranging from computation, image and video manipulation and storage. We’ll be looking solely at the storage test here.
On PCMark 7, the SSD 850 Evo managed slightly improved scores over its predecessor. The old SSD 840 Evo was not shabby, but the SSD 850 Evo now closes the gap between Samsung's mainstream and high-end drives. Its score of 5583 points marks an improvement of around 2%. Compared to the Crucial drives, it scored about 4% more. Looking at the breakthrough of the score, we can see that the SSD 850 Evo’s performance across all scenarios was respectable and consistent.
CrystalDiskMark 3.0.1 Results
CrystalDiskMark is an easy-to-run and quick utility to use to gauge a drive’s performance. It measures sequential read and write performance and random read and write speeds of random 4KB, 4KB (queue depth 32) and 512KB data.
On CrystalDiskMark, the SSD 850 Evo’s speeds was mostly very comparable to the older SSD 840 Evo - especially on the sequential, 512K and 4K read and write workloads. However, we noticed a substantial improvement in write performance when it came to more intensive 4K, 32 queue depth workload. This was the Achilles’ heel of the SSD 840 Evo as its TurboWrite cache was insufficient to boost performance. However, the new SSD 850 Evo was able to overcome this and its performance on this demanding workload was in fact comparable to even the high-end Samsung SSD 850 Pro and SSD 840 Pro.
AS SSD 1.7.4739 results
AS SSD is a benchmark that uses non-compressible and completely random data. What this means is that the drives using the SandForce SF-2281 controller cannot compress the data first, which takes away one of the strong advantages of this controller. Therefore, this is a useful benchmark because drives that use the SF-2281 controller or similar won't gain an upper hand.
Samsung’s controllers have always been adept at handling non-compressible data and so it should come as no surprise that their performance on AS SSD has always been stellar. Beginning with the Copy Benchmark, we can see that the new SSD 850 Evo is almost on a par with Samsung’s flagship SSD 850 Pro, and also offers improved overall performance when compared to the SSD 840 Pro and SSD 840 Evo. It is also handily faster than both the Crucial drives and even Plextor’s M6 Pro.
Moving on, we can see that the SSD 850 Evo offers more performance over the SSD 840 Evo especially in the intensive 4k, 64 threads workload. Read performance has gone up by around 30%, whereas write performance too has been improved by around 22%. However, in this workload, we can see that the SSD 850 Evo’s write performance starts to dip as its TurboCache cache runs out of memory to maintain performance.
Iometer results (Part 1)
Lastly, we put the drives through the rigorous grind of Iometer, with different workloads and I/O queue depths. We have chosen to show results from a queue depth of 1 to 5 as this better represents the workloads a typical consumer might face.
Iometer’s intensive workloads are problematic for mainstream drives like the Samsung SSD 850 Evo, but overall, the drive manages well. Read performance starts off poor, but picks up with increasing queue depth, but more importantly, write performance has been significantly improved. Performance on the File and Web server workloads continue to be disappointing, especially when compared to the Crucial MX100 and M550.
Iometer results (Part 2)
Finally, we look at the I/O response times for the workloads reported on the previous page. TLC NAND inherently suffers from latency issues (arising from the need to check more voltage states), but like its predecessor, the SSD 850 Evo manages to overcome this well, thanks to its TurboWrite cache technology. However, the TurboWrite cache does have its limitations and can be exhausted when it comes to highly intensive workloads, such as the File and Web Server workloads. When it does, performance suffers quite dramatically. Fortunately, such work scenarios are typically not something that mainstream users would subject their drives to.
Making 3D V-NAND affordable
Samsung is a true giant in the SSD market and is currently the only brand that designs and manufactures all aspects of a drive - controller, NAND and firmware. Only Toshiba, with the acquisition of OCZ, comes close, but they have yet to fully take advantage of their synergy to challenge Samsung in this space (2015 could be interesting, but that's another story). As such, Samsung enjoys a unique position in the SSD market.
As we mentioned in our review of the SSD 850 Pro, the implications of 3D V-NAND and the potential of it is tremendous. The SSD 850 Pro is proof that stacking cells has significant performance and endurance benefits, and is the key towards creating higher capacity SSDs as current technologies in NAND lithography reaches a point of diminishing returns. Now, the SSD 850 Evo takes 3D V-NAND even further by attempting to bring down the cost of entry for consumers to enjoy this new NAND architecture.
On the performance front, the SSD 850 Evo offers improved performance but continues to be hampered by some of the inherent shortcomings of TLC NAND. The new MGX controller, despite having just two cores as opposed to three cores of the MEX controller, performs well enough to give the SSD 850 Evo better write performance than its predecessor. However, like its predecessor, the SSD 850 Evo's write performance is heavily dependent on its TurboWrite cache. For most instances, the cache is large enough to sustain performance, but once the cache is exhausted, performance starts to dip quite drastically as we saw on the AS SSD and Iometer benchmarks. Still, one must remember that such scenarios are not typically what mainstream users would subject their drives to, so for most users this should not be much of an issue.
The SSD 850 Evo has big shoes to fill and while performance and endurance has been improved, its price has also increased significantly and we are not sure its as attractive as its predecessor.
As for cost, depending on where you shop, the SSD 850 Evo has a street price of around S$219. This means a premium of roughly $35-$40 or 20% over the SSD 840 Evo, which is definitely significant as the market for SSDs is highly price sensitive. For that extra money, you get improved performance and a longer 5-year warranty, but we are not sure this is enticing enough for most users.
Furthermore, at that price the SSD 850 Evo has to go up against drives like the Crucial M550 and Plextor M6 Pro. Though these two drives are not any faster, but because they employ regular MLC NAND, they are more consistent overall especially when it comes to write performance. We would also argue that for a bit more money ($30 or so more), one should also consider last generation’s SSD 840 Pro, which is still being sold at some places and is still a top notch high-end drive.
What we are trying to say is that as a mainstream SSD, the SSD 850 Evo is not quite as compelling as its predecessor, which combines excellent performance and a very attractive price tag. However, one must remember that the SSD 850 Evo has very big shoes to fill considering the cult following its predecessor enjoys. Nevertheless, it represents a starting point for more affordable 3D V-NAND drives. After all, it is only a matter of time before volume production picks up and the price of TLC 3D V-NAND (and the SSD 850 Evo) falls.
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