Samsung SSD 850 EVO (120GB, 250GB, 500GB & 1TB) Review
by Kristian Vättö on December 8, 2014 10:00 AM ESTEndurance: Close to Planar MLC NAND
The big question with every new NAND generation is the endurance. We already saw 6,000 P/E cycles in the SSD 850 Pro and an amazing 40,000 P/E cycles in the SSD 845DC Pro, which proved that V-NAND provides substantially better endurance over today's planar NAND nodes. However, endurance was never really an issue with planar MLC NAND except in the enterprise space, so the 850 EVO with its TLC V-NAND offers a much more interesting insight to the capability of 3D NAND technology.
To test endurance, I put the 120GB 850 EVO through our usual endurance test suite. Basically I just used Iometer to write 128KB sequential data at queue depth of 1 to the drive while monitoring the Wear Leveling Count (WLC) and Total LBAs Written SMART values. The 'Current Value' of the WLC SMART value gives the remaining endurance as a percentage (starts from 99), whereas the 'Raw Data' value indicates the number of consumed P/E cycles. In order to estimate the endurance, I had to find the spot where the increase in 'Raw Data' value decreases the 'Current Value' by one.
| Samsung SSD 850 EVO Endurance | |
| Change in Current Wear Leveling Count Value | 6 |
| Change in Raw Wear Leveling Count Value | 128 |
| Total Data Written | 15,260GiB |
| Estimated Total Write Endurance | 254,325GiB |
| Observed Number of P/E Cycles | 1,987 |
It appears that TLC flavor of V-NAND is rated at about 2,000 P/E cycles. The raw WLC value seems to be based on the user capacity (i.e. 120GB = 1 P/E cycle) because just going by it puts the endurance at ~2,133 P/E cycles (128/0.06), but that doesn't add up with the raw NAND capacity and total data written. However, the estimated total write endurance (which is just 15,260/0.06) suggests that the NAND itself is rated at 2,000 P/E cycles, which would make sense as the number of P/E cycles is usually an even thousand and it's also inline with the increase that the 850 Pro saw (from 3,000 cycles in the 840 Pro to 6,000 cycles).
| Samsung SSD 850 EVO Lifetime Estimation | ||||
| 120GB | 250GB | 500GB | 1TB | |
| Raw NAND Capacity | 128GiB | 256GiB | 512GiB | 1024GiB |
| NAND P/E Cycles | 2,000 | |||
| Raw NAND Endurance | 250TiB | 500TiB | 1000TiB | 2000TiB |
| Lifespan with 20GiB of Host Writes per Day with 1.5x Write Amplification | 23.4 years | 46.8 years | 93.5 years | 187.0 years |
| Lifespan with 100GiB of Host Writes per Day with 3x Write Amplification | 2.3 years | 4.7 years | 9.4 years | 18.7 years |
While write endurance in client workloads was never truly an issue even with planar TLC NAND, the doubled endurance in TLC V-NAND makes it practically impossible to wear out the drive before it has become totally obsolete. Only some very extreme workloads could wear out the smaller capacities before the warranty runs out, but the 850 EVO is a wrong drive for such workloads in the first place. All in all, there should be absolutely no reason to worry about the endurance of the 850 EVO, especially given the endurance ratings Samsung is giving to the 850 EVO (75TB for 120/250GB and 150TB for 500GB/1TB).
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R3MF - Tuesday, December 9, 2014 - link
my mistake, i had presumed that the Pro was not a consumer part.still, six months on with the arrival of tons of X99 and Z97 boards sporting m.2 slots, and the drives based on the marvell controller just months away, i'd have thought it would merit a mention.
hojnikb - Tuesday, December 9, 2014 - link
There is a separate article adressing this....cm2187 - Tuesday, December 9, 2014 - link
But out of curiosity, what are you going to do with the extra performance? Who actually has any use specs higher than what the EVO already offers. It is certainly the case on some heavy load server but for end users, even enthusiasts like me, I am not sure I would get an even slightly better experience by beating the SATA 3 specs.R3MF - Tuesday, December 9, 2014 - link
I presume that SATA express and m.2 were invented for no reason then?Bandwidth is useful, as is lower latency.
cm2187 - Wednesday, December 10, 2014 - link
Well, it's not because it is invented that it is useful. It's like having dozen of cores in a CPU. Some applications will have some use for these cores (certainly relevant on servers or for virtualization). But the vast majority of common applications are single threaded so people should rather focus on higher clock rates. I'm always happy to see higher specs but I just wonder which of my application will be faster with M2.Supercell99 - Sunday, December 14, 2014 - link
Virtualization. I run VMware with several OS's running at the same time on my desktop. Being able to startup and have these run off a low latency disk is nice. Power users always have a need for high bandwidth, low latency I/O.hojnikb - Wednesday, December 10, 2014 - link
These can be used for PCI-E or SATA protoco. In fact, most m.2 drives run sata instead of pci-edcaxax - Tuesday, December 9, 2014 - link
I'm unconvinced by Samsung. My SSD 830 is doing ok, having suffered an acceptable 30% performance decline (which may be correctable via secure erase but I will not test this).But my 840 (non-EVO) which works in my HTPC and sees limited use outside of the hibernation file (60 of the drive is empty by the way) is now running more than 60-70% slower.
This is just unacceptable in a system which supports trim (win 7 x64). Samsung have done nothing to rectify this, claiming these problems occur on their EVO line. Until they change their approach, I'm inclined to distrust their latest cost-saving "innovation" and give my money to crucial instead.
simonpschmitt - Tuesday, December 9, 2014 - link
Dear Mr. Vättö,while I don't think it would necessary belong into this article R3MF has a point. What is the state of SATAExpress, NGFF, m.2, ... currently? My laptop is 18 Month old and has an unuses m.2-slot witch, to my knowledge, nobody ever put an SSD into. You seem to have an ear to the ground when it comes to the SSD-Industry. There are a few questions you might have a qualified opinion about:
- Will we be seeing current-gen (meaning 850 EVO-gen) m.2/SATAExpress SSDs?
- If yes, up to wich capacity in wich form factor (2242, 2280, ...)?
- with regards to m.2: Will there be mainly PCIe (2 lanes/4lanes) drives or SATA?
- When do you suppose these will be an economically viable alternative to 2.5" given both slots are available?
In your personal opinion:
- What is the point of SATAExpress when literally every SATAExpress-Device also has m.2?
- Will there be a subjective improvement for the normal or enthusiast (non Datacenter) user with the switch to PCIe?
A quick blurb, perhaps in the form of a short pipeline aticle, would be much appreciated.
An other thing I always wondered about: While I am amazed with the percieved benefits of an SSD vs. an HDD game-load-times often seem not to change at all. It's more of an oddity than a real concern but my new system (i5 4200, 8GB, 840 EVO) often has the same load times than my old system (i3 330, 4GB, HDD). I always thought load times were mainly dependent on how fast the data can be read (HDD/SDD bound) and how fast it can be processed/extracted (CPU bound). Is there a factor I'm missing or do games just not take advantage of certain kinds of faster hardware.
Perhaps you or some of the other readers can help me with my curiosity.
Thanks, Simon
metayoshi - Tuesday, December 9, 2014 - link
I can't answer all of your questions, but I can answer the gaming part.With regards to gaming, it really depends on the game. Many games these days are relatively optimized on loading, so running them on an HDD or SSD doesn't matter too much since they like to load parts of the game in the background. However, there are some games where having an SSD is completely noticeable. As an avid World of Warcraft player, I can tell which raid members have SSDs and which don't because those of us with SSDs simply appear in the raid much faster than those on HDDs when switching zones. I mean, it definitely doesn't hinder gameplay too much since the only thing that takes a while is actually getting into the zone. The rest of the zone is in RAM already, so getting to and fighting bosses are instantaneous. I used to have a 7200 RPM drive before too. For me, the difference is completely noticeable now that I have had an SSD for a couple of years now.