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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  • Timur Born - Sunday, July 28, 2013 - link

    I am not convinced about that yet, especially since you can turn off drive cache flushing via Device-Manager and thus should get an even more aggressive Windows cache behavior than what RAPID offers (which is reported to adhere to Windows' flush commands).

    The Windows cache is designed to keep data in RAM for as long as it's not needed for something else. Even more important, data is *directly* executed from inside the Windows cache instead of being copied back and forth between separate memory regions. This keeps duplication to a minimum (implemented since XP as far as I remember). So at least for reads the Windows cache is very useful, especially in combination with Superfetch, which is *not* disabled for SSDs btw (even Prefetch for the boot phase isn't disabled, but in practice it makes not much of a difference whether you boot with or without Prefetch from an SSD).

    There is something funky going on with Windows' cache and the drive's onboard cache of my Crucial M4 in combination with ATTO (Windows cache enabled). Different block sizes get very different results, with some *larger* block sizes not benefiting from Windows' cache either at read or write, the latter depending on the block size chosen. Turning the drive's own cache flushing on/off via Device-Manager can have an impact on that, too.

    In some cases I get less throughput with Windows cache than without (i.e. 512 kb block size with drive flushing on). This may be an issue of ATTO, though, because I also got some measurements where ATTO claimed a write speed of zero (0)! Turning off either drive cache flushing or the Windows cache or both helps ATTO to get meaningful measurements again.

    So the main question remains: How and why would RAPID affect "real-world" performance on top of the Windows cache and does the Anand Storage Bench deliberately circumvent the Windows cache?

    The reason I was looking at this review was that I am currently looking for a new SSD to build a desktop PC and the 840 EVO looks like the thing to buy. So once I get my hands on one myself I will just try RAPID myself. ;)
    Reply
  • Timur Born - Sunday, July 28, 2013 - link

    Just did a quick test: On my 8 gb RAM system Windows 8 uses quite exactly 1 gb for write caching and all available RAM for read caching. It doesn't matter whether the 1 gb consist of one or several files and whether they fit into the cache as a whole or not (first 1 gb is cached if not). Reply
  • 1Angelreloaded - Friday, July 26, 2013 - link

    Hold on a second correct me if I'm wrong on this paradox. Did Samsung not scale back on NAND production in order to drive the price up for greater bloated profits, now as stated in Korea press conference they want "SSDs for everyone". WTF is going on here, and why are SSDs not at more reasonable pricing by now about .33cents per gig.?They had a complete shot at burying HDDs after the flood and the price hike. Reply
  • FunBunny2 - Friday, July 26, 2013 - link

    Don't confuse capitalists with intelligence. They look at unit margin and ignore gross profit. IOW, they'd rather sell 100 at $2 margin than 1,000 at $1 margin. They're stupid. Reply
  • MrSpadge - Saturday, July 27, 2013 - link

    There's also the factor of marget saturation to take into account. You can't sell an infinite number of drives. Reply
  • Notmyusualid - Friday, July 26, 2013 - link

    Exciting technology indeed! Impressive numbers, nice identification of spare computer resources, and put to good use too. I'd imagine this would be the go-to drive for most users...

    But I'd like my clocks available for my applications thanks.

    In addition, I'm not willing to put my data on any non-enterprise disk now, cost be damned. Burned too many times now.

    Interesting product though....
    Reply
  • z28dreams - Friday, July 26, 2013 - link

    I recently saw the Plextor M5P (pro) for $190 on sale.

    If the 840 evo comes out in the same price range, which would be a better buy?

    It looks like the write seems of the M5P are better, but I'm not about overall performance.
    Reply
  • K_Space - Friday, July 26, 2013 - link

    Help a noob here: How is Rapid any different to a custom nonvolatile RAM disk with your selected cached files stored on it & these being written to the SSD at an interval? Is it mainly because Rapid can writes in blocks and it's more intelligent in its choice of cached files? Reply
  • wpapolis - Saturday, July 27, 2013 - link

    Hey there all,

    I have a MacBook 13" from late 2008, the first gen of the unibody construction (Model MB467*/A).

    My bus speed is SATA 3Gbit/s.

    What's the best SSD for me?

    Trim doesn't work automatically for me, though I have found the commands to use in terminal to enable it.

    This Samsung drives looks really good, but it seems like I won't be able to use RAPID, or perhaps even TRIM. Plus I am limited by my bus speed. Should I still go for this Samsung just because the price might be the same as lower featured alternatives?

    What do you guys suggest? I want one in the 250GB range.

    Thanks,

    Bill
    Reply
  • TheinsanegamerN - Saturday, July 27, 2013 - link

    if you have a mac, the samsung is your best bet. TRIM can be enabled quite easily on a mac if it is not done automatically, so you can use trim. as for RAPID, it replaces window's terrible i/o caching process. osx does not have this problem, so you dont have to worry about that. now, the sata2 interface will be a bottleneck, but it will still be much faster than a hard drive. id go for either this evo drive or the 840 250gb Reply

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