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Results: Write Endurance Testing

Samsung 845DC EVO SSD Review: 3-Bit MLC Hits The Enterprise
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Over the past few years, we've added a lot of write endurance testing to our benchmark suite. The rise of read-focused enterprise drives made those metrics even more important. Fortunately, during the last 12 months, testing enterprise SSDs standardized partly due to the introduction of JEDEC's JESD218A write endurance testing standard. Instead of issuing vague ratings, we now see companies specifying their drives to JESD218A, which uses the JESD219A enterprise workload to quantify endurance. The good news from all of that is that this closely matches the types of workloads we use in our Enterprise Workload Performance tests.

Previously, our write endurance testing consisted of large block sequential writes, which is completely different from the JEDEC standard. Still, it gives us valuable information about P/E cycles and allows us to compare SSDs at a NAND level, reducing the effects of flash controller optimizations and over-provisioning. Write amplification is also reduced so that we don't incur any additional NAND writes beyond what we intend.

For this test, we use the 240 GB model and monitor SMART attribute 177, which is the wear leveling count. It's a normalized value meant to show a percentage of life remaining on the drive. We took multiple percentage points off of the drive and compiled the results. We then extrapolated the number out to a full 100% usage; the following numbers are what we ended up with:

Endurance Rating
Sequential Workload, QD=1, 8 MB
Samsung 845DC EVOIntel SSD DC S3500
NAND Type
Samsung 19 nm 3-bit MLC
Intel 20 nm MLC
Raw NAND Capacity
256 GB
528 GB
IDEMA Capacity (User Accessible)
240 GB480 GB
Over-Provisioning
12.7%15.5%
P/E Cycles Observed (IDEMA)
3643
3651
P/E Cycles Observed (Raw)
3181
3097
Host Writes per 1% of MWI
7.95 TB
15.97 TB

As you can see, the 845DC EVO actually does get more P/E cycles (according to SMART) with Samsung's 3-bit MLC than we observed from Intel's SSD DC S3500.

Does that sound too good to be true? Let's change things up a but, then. Instead of using large block sequential writes, we'll go with 4 KB random writes instead, which should get closer to the JEDEC specification and apply more stress to the NAND/controller. Also, in this test we'll use the 960 GB model to see if the difference in over-provisioning matters.

The 687 TBW result ends up being mostly the same. Still, you're getting almost 15% more than Samsung's 600 TBW specification. That doesn't come anywhere close to eMLC flash or some of the optimized MLC-based solutions from SanDisk and Micron, but considering the price and target segment, it is more than adequate.

I'm also not taking into account that many review sites, including this one, have already pushed their consumer 840 EVO drives far beyond the point at which the wear leveling count hits zero. We hope our testing helps convince some of the doubters, but we can appreciate skepticism amongst a high-end audience.

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  • 3 Hide
    SteelCity1981 , June 2, 2014 6:28 AM
    So basicly it's the more durable version of the 840 evo much like opertons and xeons are to the FX and core i7 series.
  • -8 Hide
    Plusthinking Iq , June 2, 2014 6:48 AM
    like we know now after the ssd endurance test samsung is the worst enterprise candidate.
  • 3 Hide
    drewriley , June 2, 2014 7:43 AM
    Quote:
    So basicly it's the more durable version of the 840 evo much like opertons and xeons are to the FX and core i7 series.


    Yes, that's a fair analogy. Just like the Xeon E3-1275v3 is an i7-4770K, but with ECC support.

  • 2 Hide
    damric , June 2, 2014 12:45 PM
    I've yet to see an SSD fail due to read/write endurance. I only see them fail when the controller gets bugged, which seems to happen all the time, especially on loss of power.



  • 0 Hide
    soundping , June 2, 2014 1:13 PM
    I'm guessing this SSD doesn't have to new firmware code that extends life and speed.
  • 0 Hide
    jase240 , June 2, 2014 3:02 PM
    Another win for the EVO. This SSD modified for enterprise workloads makes it a good buy for webservers.

    Hopefully the price will go down after launch, and then I see this being the best choice of webhosts.

    Cheaper and adequate for that workload.
  • 0 Hide
    Nightmare Twily , June 2, 2014 5:18 PM
    Eh I'll keep my 840 EVO 250GB
  • 0 Hide
    Nuckles_56 , June 3, 2014 4:12 AM
    "Even still, I wand to commend Samsung's execution." (last page 1st paragraph) I guess that is supposed to be want, unless Drew Riley has become a wizard now :D 
  • 0 Hide
    Menigmand , June 3, 2014 7:07 AM
    Commending their execution would be a bit harsh, don't you think?
  • 0 Hide
    drewriley , June 3, 2014 8:31 AM
    Quote:
    Commending their execution would be a bit harsh, don't you think?


    I'm sure worse things were said about Samsung at WWDC '14 yesterday ;) 
  • 0 Hide
    drewriley , June 3, 2014 8:33 AM
    Quote:
    "Even still, I wand to commend Samsung's execution." (last page 1st paragraph) I guess that is supposed to be want, unless Drew Riley has become a wizard now :D 


    Now that you mention it.....
  • -1 Hide
    eriko , June 3, 2014 9:53 PM
    4KB random write, and average response time.

    Nuff said.

    You'd have to be out your mind to put TLC in a a critical environment.
  • 1 Hide
    patrick47018 , June 3, 2014 10:30 PM
    @eriko everyone's critical environments need a little tender loving care
  • 1 Hide
    photonboy , June 4, 2014 5:28 PM
    The 845dc isn't necessarily the "worst enterprise candidate"; for one thing it wasn't the bottom in every test.

    For another, it's more about VALUE and that's the main point of the article. I assume the top SSD's in this category were MLC not TLC and also more expensive.