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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  • eanazag - Monday, December 8, 2014 - link

    Turbowrite is a default feature. It is marketing speak for optimizations to increase write performance in write workloads. It can't be turned on or off. Reply
  • erple2 - Wednesday, December 10, 2014 - link

    Well, it has to be able to be turned on/off, as Kristian has a chart showing the difference in write speeds with it on/off. However, unlike "RAPID", there is no downside to leaving it on. Reply
  • geniekid - Monday, December 8, 2014 - link

    Well written conclusion. Reply
  • andrewbaggins - Monday, December 8, 2014 - link

    It's hard to understand why your SSD reviews fail to include Idle Power Consumption charts. For the hundreds of millions of PCs and laptops in use which do not support the so-called Slumber Power it would be far more useful if you included a chart for typical or average power consumed during Idle state. Reply
  • metayoshi - Monday, December 8, 2014 - link

    "Hundreds of millions of PCs and laptops in use which do not support the so-called Slumber Power."

    Woah... I don't know where you got that "hundreds of millions" number from, but any system that supports SATA is able to support Slumber. Slumber has been in the SATA spec since forever, and pretty much all 2.5" drives, and some 3.5" drives support this power state.
    Reply
  • metayoshi - Monday, December 8, 2014 - link

    P.S. As an example, I have a Core 2 Quad Q6600 sitting in my cubicle at work on an Asus PSE WS Pro motherboard. I have no Idea how old this thing is, but it's running a SATA-II 3.0 Gbps interface, and that great grandfather of a system supports HIPM+DIPM, and does Partial and Slumber on a variety of SSDs and HDDs. Reply
  • eanazag - Monday, December 8, 2014 - link

    Newegg has a promotion for these drives ending 12/14/14 (US $) -
    120GB @ $89.99
    250GB @ $139.99
    500GB @ $249.99
    1TB @ $469.99
    Reply
  • eddieobscurant - Monday, December 8, 2014 - link

    I think an 120gb 850 evo usb thumb drive would be awesome . Reply
  • dwade123 - Monday, December 8, 2014 - link

    Realworld: all modern ssds have similar windows boot and game loading time. All these synthetic tests are just for reviewers to have something talk about, and marketing purposes. Meh. Reply
  • StrangerGuy - Monday, December 8, 2014 - link

    I would rather want a SSD that has 90% of a MX100 but only 50% dollar per GB, instead of extra performance that 99% of SSD buyers will not never benefit for more money. Reply

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