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
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  • hojnikb - Monday, December 8, 2014 - link

    Or 50$ less and get a mx100/ultra II Reply
  • apoe - Tuesday, December 9, 2014 - link

    $10 more than the 250GB 850 Evo and you can get a 480GB Crucial M500 or TWO Sandisk Ultra II's. Even though it's a year and a half old at this point, for most end users the speed difference is negligible but the doubled capacity is not. Like the article says, the pricing (at least the MSRP) seems to be in a weird place... Reply
  • HisDivineOrder - Wednesday, December 10, 2014 - link

    Samsung thinks they're Apple.

    In SSD's.
    Reply
  • alacard - Monday, December 8, 2014 - link

    thanks for the review. is it my imagination or is the 120gb model missing from the destroyer benchmark? Reply
  • Kristian Vättö - Tuesday, December 9, 2014 - link

    I don't usually run the 2013 suite on 120/128GB drives because it's more geared towards large and higher performance drives. Users with such heavy workloads shouldn't be buying small drives anyway for performance and capacity reasons. Reply
  • Memristor - Monday, December 8, 2014 - link

    Regarding the price, newegg.com already offers them below the suggested retail price. See here:
    http://promotions.newegg.com/samsung/14-6480/index...
    Reply
  • wallysb01 - Monday, December 8, 2014 - link

    Only by $10. That’s not really enough. I got the 480 GB Ultra II for $160 over black Friday, that’s $90 less than this sale on the 500GB 850 EVO. That was maybe an atypically good deal, but even at more regular discounts the Ultra II/MX100 is priced at about $180-$190, maybe $200, which is more like $50-$70 less than this “sale” price 850 EVO.

    This review is right. Until the price comes down ~$50 per 500GB, I don’t see much reason for people buy the 850 EVO.
    Reply
  • fokka - Monday, December 8, 2014 - link

    comparing msrp to a black friday deal doesn't make sense. Reply
  • Luscious - Monday, December 8, 2014 - link

    Where's the m.2 version?

    And if Samsung is stubbornly sticking with 2.5 inch drives, why no Sata Express version?

    The hardware for both is out there, and has been for some time.
    Reply
  • ZeDestructor - Monday, December 8, 2014 - link

    It's a SATA drive, so the interface will be SATA and not SATA Express/PCIe. Consequently, an M.2 variant will perform the same, since those variants would also be SATA driven, much like the older mSATA drives - same thing, different form factor, and unnecessary to review seperately. Reply

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