Endurance: 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).

Three Bits and Three Dimensions: What's the Deal? Performance Consistency & TRIM Validation


View All Comments

  • Kevin G - Monday, December 8, 2014 - link

    What version is the firmware of the 840 EVO? There is a notorious bug out there that'll drastically reduce the speed of the drive when it attempts to read data.

  • romrunning - Monday, December 8, 2014 - link

    That's the bug about reading really old data. If he did an upgrade, then it wouldn't be really old data on the new drive.

    It also doesn't apply to the point he was making - would I subjectively "feel" the difference if I upgrade to the 850 EVO from an older <insert_brand_here> SSD?
  • doggghouse - Monday, December 8, 2014 - link

    On one of these review sites, they mentioned that the step up from HDD to SSD is enormous, but between the different generations of SSD the difference isn't nearly as noticeable. Depending on the test, the difference between HDD and SSD is anywhere from 2.5x faster (ex. sequential write) to 140x faster (ex. random write). You definitely will not see such a marked improvement going from one SSD to another.

    Also I agree with your point about the benchmarks being pointless for the average user. A lot of the benchmarks are geared towards enterprise usage. I think part of the problem is that the drives all behave pretty similarly (compared to HDD anyway), until they are pushed to the extremes. That's the only way for the reviews to differentiate between them, unless they find a particular weak point or flaw.
  • eanazag - Monday, December 8, 2014 - link

    The performance profile of the drives and your workload will dictate if you notice the better performance. I would guess that you got a lot more GBs/$ when you picked up the Evo versus the Corsair drive. Also, not you don't need to struggle to get everything on to your boot drive. At the same time your computer may only startup 2 or 3 seconds faster.

    They don't for an average user, but if you're here there's a good chance you're not an average user. And those fancy benchmark numbers cost you what?

    There are real life workloads that will benefit for an average user. I have seen the consistency play out in my usage in various drives. I have seen garbage collection routines cause some painful performance issues in software encrypted drives.
  • MrSpadge - Monday, December 8, 2014 - link

    With a half-decent SSD your I/O is probalby mostly CPU-limited in the real world anyway. Reply
  • ummduh - Monday, December 8, 2014 - link

    In my opinion, the best reason to continue to upgrade, is capacity increases.

    My first drive was 60GB, my second is 120GB, looks like my third is going to be 250GB....

    No the speed difference isn't that drastic once you get off the HDD, but now you can start keeping more and more stuff on a drive at the same price point. All of my drives have been at the $150 point.. (Ok, so I had 3 different 60GB drives, but that was due to not realizing how bad OCZ suuuuuucked and I kept going back like a moron)
  • cm2187 - Tuesday, December 9, 2014 - link

    The other thing is that most SSDs now are limited by the SATA interface. And to be honest, unless you are running a database with thousands of queries per seconds, beating the SATA interface won't really add much to your experience. Larger capacities I think would be more useful. Reply
  • Badelhas - Thursday, December 11, 2014 - link

    Thats exactly what I always think when I read this reviews. Altough they are great to read, for someone who already has a SSD the gains are not noticeable. I have a Vertex 3 120Gb that I bought in 2011 and been questioning myself if I would se any real gains going to a 840 Evo, for instance, since they are much newer but you just answered my question ;) Reply
  • matej_eu - Thursday, June 25, 2015 - link

    I am in a similar situation. My first SSD was the ADATA's SP600@64GB running on SataII, I was so mesmerized by the speed of everything (boot time, installation, app run in time, ...). I really do take care of my Win installation, drivers, and apps, but in the end size was to small for boot+main drive in laptop. I bought Samsung 840 EVO@120GB, and in the recent times I thought I was going crazy, system was noticeably slowing down. I googled, and what do you now, problems, no more Samsung EVOs for me!! Buy Samsung 8x0 PRO or some other brand. Reply
  • milli - Monday, December 8, 2014 - link

    Your Intel SSD 730 prices are wrong. They might have gone up.
    The price of the ARC 100 is amazing ATM. It scores very good in the '2013 Storage Bench service time' which in my experience tells the most about how SSDs feel in actual usage.

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