understanding total writes values on SSD

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  1. Posts : 4,173
    Windows 11 Pro, 22H2
       #11

    cereberus said:
    On nvmes, the SMART endurance record is described as:

    A value of 100 indicates that the estimated endurance of the NVM in the NVM subsystem has been consumed, but may not indicate an NVM subsystem failure. The value is allowed to exceed 100. Percentages greater than 254 shall be represented as 255.

    So, it just proves the endurance limit is meaningless really. I believe it is really a scam by vendors as you are almost certainly bound to reach 100% without failure, then even if drive did fail e.g. at 101%, they avoid warranty claims in warranty period, saying you have reached guaranteed limit of endurance.
    I've read an article where a number of SSDs were tested to the point of failure. Every single one of them went well beyond the stated endurance ratings, some of them going multiple times the TBW rating.

    However, I wonder if the manufacturers set their TBW ratings under worst case scenarios such as under very elevated temperatures.

    Naturally, you would expect the drive to last beyond the rated TBW rating since that is the absolutely minimum expected life that the manufacturer is willing to guarantee.
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  2. Posts : 14
    Win10
    Thread Starter
       #12

    Thank you all for your input.

    The SMART values are the same whether I use the manufacturer's software or any of the programs you have suggested.

    Still, no feedback on why the number of NAND writes is lower than the number of total host writes? If accurate, this seems to go against the write amplification effect.
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  3. Posts : 4,173
    Windows 11 Pro, 22H2
       #13

    justtesting said:
    Thank you all for your input.

    The SMART values are the same whether I use the manufacturer's software or any of the programs you have suggested.

    Still, no feedback on why the number of NAND writes is lower than the number of total host writes? If accurate, this seems to go against the write amplification effect.
    Unfortunately, that is not one that I can answer. Some questions in my mind that I don't have the answers to:

    Is it possible that this is a result of the wear-leveling, garbage collection, and TRIM features of the SSD controller? I don't know, but I'd be curious if those affect this.

    Also, I realize that you may really be curious about those values, I know that I am, but you may want to avoid getting caught up in those details. At least for me (you may view this differently and that's okay), the takeaway is that your SSD should still have a long life ahead of it and all is well at this time.

    I'll try my best to research this a bit further, but there are no guarantees that I will succeed in getting the answers.
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  4. Posts : 14
    Win10
    Thread Starter
       #14

    Thank you, hsehestedt.
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  5. Posts : 525
    Windows 10
       #15

    justtesting said:
    Good day.

    Crystal Disk Info shows values for Total Host Writes and Total NAND Writes on an SSD. I was wondering if the lower of those two values is a subset of the other value. Thank you for your attention.
    If the SSD has a DRAM, the writes to it are not included in the NAND writes.
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  6. Posts : 2,800
    Windows 7 Pro
       #16

    Some drives uses Static SLC in a staging area, outside of user space, and is dedicated for the lifetime of the device.

    As such it has a separate garbage collection (GC) and wear-leveling zone from the native flash, which is different than how dynamic SLC region operates.

    The wear on the drive is therefore the worse of two factors in the static SLC zone, since all the native TLC zone Writes will go to SLC first and if they do not end up being committed to TLC, there is no effective wear.

    So it's possible to have more host than TLC NAND writes for a total Wear Amplification Factor of <1.0 with these kind of architecture.
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  7. Posts : 525
    Windows 10
       #17

    SLC cells are also NAND cells, but it´s possible that the writes to them are not included in the "NAND" count.
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  8. Posts : 4,173
    Windows 11 Pro, 22H2
       #18

    @MaloK and @Anibor,

    Thanks for the additional information. That was something that I had not taken into account, so I've learned something. Makes perfect sense since SLC has a far greater number of write cycles than does MLC, TLC or QLC cells.
      My Computers


  9. Posts : 14
    Win10
    Thread Starter
       #19

    Thank you all for your input.

    I will report back when I reach the 66 TB written mark in a few years (half-joking) ... although who knows if I may be using Linux Mint or ReactOS by then. Take care.
      My Computer


 

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