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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  • TEAMSWITCHER - Monday, December 8, 2014 - link

    I'm in complete agreement. I'm not going to buy another 2.5" SSD before I can get an 850 Pro (512 GB) equivalent with an M.2 interface. I have two motherboards with empty M.2 slots waiting for the market to catch up. I know about the XP941, but the pricing isn't great. M.2 drives should cost almost the same as a 2.5" drive...especially after eliminating the worthless metal/plastic box. Reply
  • extide - Monday, December 8, 2014 - link

    Seems to me like TLC will become the standard mainstream for 3D/VNAND, where as MLC will be pretty much only for high end/enterprise, somewhat like SLC was back in the day. Reply
  • MadDuffy - Monday, December 8, 2014 - link

    Newegg prices (USD) are up:
    120 GB - 90
    250 GB - 140
    500 GB - 250
    1 TB - 470

    Email I received indicates these are promotional prices available through Dec 14th
    Reply
  • casperes1996 - Monday, December 8, 2014 - link

    Last page, fifth paragraph, last line:
    "If I was"
    Should be: "If I were"

    I know I'm a cunt for pointing it out, but I only do so because I generally think Anandtech offers fairly decently written articles, and I care too much about this sort of piss...
    Sorry.
    Reply
  • apudapus - Monday, December 8, 2014 - link

    How is data retention with this type of TLC NAND? Can the drive be powered off for a week or a month before data gets corrupted? While the drive is powered on, I assume there are refresh features for stale (a.k.a. infrequently accessed) data. Reply
  • hojnikb - Monday, December 8, 2014 - link

    If its up to jedec (i imagine it is) then its good for atleast a year. Reply
  • kgh00007 - Monday, December 8, 2014 - link

    But in reality what are they going to be like? I don't think I'll buy another Samsung TLC drive after owning the 120 GB 840 EVO for the last while! It performs erratically, especially when resuming from hibernate. It can take anywhere from 10 secs to boot, up to 5 minutes, and I have applied the latest firmware and run the speed recovery app from Samsung. I have an mSata Crucial m500 240GB which is slower on paper, but in reality is much quicker and the performance is 100% consistent, it does the same thing, every time at the same speed!!

    MLC all the way for me without any turbowrite nonsense, just straight forward advertised speeds across the whole drive all the time, without loosing data due to poor charge retention along the way!
    Reply
  • Lolimaster - Monday, December 8, 2014 - link

    Your EVO is 120 and your other drive is 240, less nand, more erratic, simple. Look at the chart, you get consistent writes/read with 500-1TB models. Reply
  • kgh00007 - Saturday, December 13, 2014 - link

    Less nand equals slower performance, not more erratic performance. But it should perform at it's given speed consistentantly. I have over 30% of the drive free and 10% set as over provisioning on the 840 EVO. There is no excuse for a 5 minute boot time with an SSD. I don't trust these Samsung drives after my experience! Reply
  • mlkmade - Monday, December 8, 2014 - link

    So I'm confused as its not very clear...Is Turbowrite turned on for all your benchmarks?

    Is turbowrite needed to hit the the 540/520 read/write times? I saw the chart with TurboWrite on and off. So with turbowrite off this drive only gets 100mb/s ?

    This article is very vague in regards to that.
    Reply

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