Endurance

Samsung isn't quoting any specific TB written values for how long it expects the EVO to last, although the drive comes with a 3 year warranty. Samsung doesn't explicitly expose total NAND writes in its SMART details but we do get a wear level indicator (SMART attribute 177). The wear level indicator starts at 100 and decreases linearly down to 1 from what I can tell. At 1 the drive will have exceeded all of its rated p/e cycles, but in reality the drive's total endurance can significantly exceed that value.

Kristian calculated around 1000 p/e cycles using the wear level indicator on his 840 sample last year or roughly 242TB of writes, but we've seen reports of much more than that (e.g. this XtremeSystems user who saw around 432TB of writes to a 120GB SSD 840 before it died). I used Kristian's method of mapping sequential writes to the wear level indicator to determine the rated number of p/e cycles on my 120GB EVO sample:

Samsung SSD 840 EVO Endurance Estimation
  Samsung SSD EVO 120GB
Total Sequential Writes 4338.98 GiB
Wear Level Counter Decrease -3 (raw value = 35)
Estimated Total Writes 144632.81 GiB
Estimated Rated P/E Cycles 1129 cycles

Using the 1129 cycle estimate (which is an improvement compared to last year's 840 sample), I put together the table below to put any fears of endurance to rest. I even upped the total NAND writes per day to 50 GiB just to be a bit more aggressive than the typically quoted 10 - 30 GiB for consumer workloads:

Samsung SSD 840 EVO TurboWrite Buffer Size vs. Capacity
  120GB 250GB 500GB 750GB 1TB
NAND Capacity 128 GiB 256 GiB 512 GiB 768 GiB 1024 GiB
NAND Writes per Day 50 GiB 50 GiB 50 GiB 50 GiB 50 GiB
Days per P/E Cycle 2.56 5.12 10.24 15.36 20.48
Estimated P/E Cycles 1129 1129 1129 1129 1129
Estimated Lifespan in Days 2890 5780 11560 17341 23121
Estimated Lifespan in Years 7.91 15.83 31.67 47.51 63.34
Estimated Lifespan @ 100 GiB of Writes per Day 3.95 7.91 15.83 23.75 31.67

Endurance scales linearly with NAND capacity, and the worst case scenario at 50 GiB of writes per day is just under 8 years of constant write endurance. Keep in mind that this is assuming a write amplification of 1, if you're doing 50 GiB of 4KB random writes you'll blow through this a lot sooner. For a client system however you're probably looking at something much lower than 50 GiB per day of total writes to NAND, random IO included.

I also threw in a line of lifespan estimates at 100 GiB of writes per day. It's only in this configuration that we see the 120GB drive drop below 4 years of endurance, again based on a conservative p/e estimate. Even with 100 GiB of NAND writes per day, once you get beyond the 250GB EVO we're back into absolutely ridiculous endurance estimates.

Keep in mind that all of this is based on 1129 p/e cycles, which is likely less than half of what the practical p/e cycle limit on Samsung's 19nm TLC NAND. To go ahead and double those numbers and then you're probably looking at reality. Endurance isn't a concern for client systems using the 840 EVO.

Inside the Drives & Spare Area TurboWrite: MLC Performance on a TLC Drive
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  • Touche - Thursday, July 25, 2013 - link

    I don't think your tests are representative of most people's usage, especially for these drives. TurboWrite should prove to be a much better asset for most, so the drive's performance is actually quite better than this review indicates. Reply
  • Sivar - Thursday, July 25, 2013 - link

    Really well-written article.
    I have to admit, while most of Samsung's products are crap, their 840 and later SSDs are not bad at all.
    (The 830, while not prone to electronic failure, was built really poorly. It's SATA connector would snap off if you tilted your head the wrong way while looking at it).
    Reply
  • Coup27 - Thursday, July 25, 2013 - link

    Samsung have gotten into the world position they are in today by selling crap. I have used plenty of 830's and I have never had an issue with the SATA connector so I have no idea what you are doing with it. Reply
  • Coup27 - Thursday, July 25, 2013 - link

    Haven't ^^ (why is there no edit button?) Reply
  • piroroadkill - Thursday, July 25, 2013 - link

    So you accidentally broke a SATA connector, and now that's suddenly a flaw? I have two Samsung 830 256GB in my system, and somehow I didn't break the SATA connectors...
    I also fitted 4x Samsung 830 256GB to a server at work.. and somehow I didn't break the SATA connectors..
    Reply
  • HisDivineOrder - Saturday, July 27, 2013 - link

    True, this. SATA connectors are poorly designed, but that's the fault of the people who made the spec, not the specific one in the 830. I'm not saying it can't break. I've had SATA connectors break on a variety of devices. None of them were my 830, but I'm not saying it's impossible or whatever.

    I've seen WD, Seagate, and Hitachi drives all have a problem with the connector, though. Seems like SATA and HDMI were designed to make the connection as loose and easily broken as possible. I guess that gives them some small percentage of people buying all new product to replace something on said product that's small and plastic...
    Reply
  • mmaenpaa - Thursday, July 25, 2013 - link

    Good article once again Anand,

    and very good perfomance for this price range.

    Regarding Torx, I believe this is one the main reasons why it is used:

    "By design, Torx head screws resist cam-out better than Phillips head or slot head screws. Where Phillips heads were designed to cause the driver to cam out, to prevent overtightening, Torx heads were designed to prevent cam-out. The reason for this was the development of better torque-limiting automatic screwdrivers for use in factories. Rather than rely on the tool slipping out of the screw head when a torque level is reached, thereby risking damage to the driver tip, screw head and/or workpiece, the newer driver design achieves a desired torque consistently. The manufacturer claims this can increase tool bit life by ten times or more"

    (from https://en.wikipedia.org/wiki/Torx)

    BR,
    Markku
    Reply
  • hybrid2d4x4 - Thursday, July 25, 2013 - link

    For what it's worth, my experience with screws is consistent with your post. I've never had a torx screw slip out, which is definitely not the case with philips or the square or flathead varieties. I'd like to see them used more often. Reply
  • piroroadkill - Thursday, July 25, 2013 - link

    Agreed. I love Torx. Philips and pozidriv are the terrible bastard children of the screw universe. Always slipping and burring. Ugh. If everything was replaced with totally cam-out free designs like Torx, allen head, robertson screw.. etc, etc.. then I'd be more than happy. Reply
  • psuedonymous - Thursday, July 25, 2013 - link

    I'd LOVE for Torx to be used more often. They're much easier to work with (not once have I had a Torx screw fall off the screwdriver and roll under the desk), the screwheads are more robust, and they frankly look a lot nicer than Philips or Pozidriv.

    It'd make pulling apart laptops all day a darn sight less onerous if Torx were the standard rather than Philips.
    Reply

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