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Which attributes are used to calculate SSD health percentage? Is there any formula to calculate SSD health percentage?

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S.M.A.R.T data for the SSD is calculated by the firmware of the SSD and published to the operating system. It is based on statistical data based on the technology used inside the SSD and certain measurements done by the manufacturer.

There is no guarantee that this estimation is valid for any one SSD. It is common for good-quality SSDs to achieve 200% life-time and even more. The basic numbers are burnt into the firmware by the manufacturer and are usually very conservative.

The SSD will most commonly make available the following three measures:

  • SSD Life Left : Supported by few manufacturers, this parameter represents calculated lifespan remaining in the disk based on certain equations. When normalized, it reads 100 (100%) for healthy drives to 1 (1%) for dead SSD’s. Sometimes replaced with Percentage of the Rated Lifetime Used.

  • Percentage of the Rated Lifetime Used : This is the opposite of SSD Time Left. 1 means the drive is 100% healthy, while 100 means that 100% of the drive’s lifetime is used up, and the drive is nearing its end of life.

  • Grown Failing Block Count : Manufacturer-specific value representing the number of reallocation events, meaning unusable blocks on the SSD. A rise in this value represents a problem with the drive.

One parameter used in the calculation is the lifetime of flash memory, on which SSDs are based, limited to 10 000 writes for most. An important task for the firmware is ensuring that all memory cells are used evenly, and monitoring how many times data was written to them, meaning how much life is left for the SSD.

Some manufacturers give the total amount of data written to the drive as one of the drive lifetime indicators. For example, Intel guarantees that the total of about 37 TB of data will be written to X25-M drives (20 GB per day for 5 years).

An SSD that is nearing its end of life according to the firmware should be treated with caution and have backups, but there is no need to panic. Some drives continue to work much beyond that time, just as others fail much sooner than foreseen.

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  • so, many softwares like hard disk sentinel, Hddlife, etc. that shows health percentage are they accurate or not. Oct 9, 2019 at 4:39
  • All these products do is report the data as given by the firmware, but as said above this data is only statistical in nature. The data should be taken seriously, so the disk shouldn't be trusted when end-of-life is near, but it may keep on working a long time after this date, or even fail before. There are no guarantees, the numbers are only estimations based on statistics.
    – harrymc
    Oct 9, 2019 at 7:08
  • Okay, so u mean all these software that are calculating health are estimate percentages and thanks. Oct 9, 2019 at 7:39
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Actually I researched and found that for HDD the following attributes affect disk health:

  1. Reallocated Sectors Count
  2. Spin Retry Count
  3. Current Pending Sectors Count
  4. Offline Uncorrectable Sectors Count
  5. Reallocated Event Count

and they have their own weight and limits.

here I found this.--- https://www.hdsentinel.com/help/en/52_cond.html

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