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I have Samsung SSDs on my own laptop and on some servers.

When I do:

smartctl -a /dev/sda | grep 177

I get results that I cannot understand. Here are some examples:

# my laptop Samsung SSD 850 EVO 500GB (new)
177 Wear_Leveling_Count     0x0013   100   100   000    Pre-fail  Always       -       0

# server 256 GB, SAMSUNG MZ7TE256HMHP-00000
177 Wear_Leveling_Count     0x0013   095   095   000    Pre-fail  Always       -       95

# server 512 GB, SAMSUNG MZ7TE512HMHP-00000 (1 year old)
177 Wear_Leveling_Count     0x0013   099   099   000    Pre-fail  Always       -       99

# server 512 GB, SAMSUNG MZ7TE512HMHP-00000 (suppose to be new)
177 Wear_Leveling_Count     0x0013   099   099   000    Pre-fail  Always       -       99

# server 480 GB, SAMSUNG MZ7KM480HAHP-0E005
177 Wear_Leveling_Count     0x0013   099   099   005    Pre-fail  Always       -       3

# server 240 GB, SAMSUNG MZ7KM240HAGR-0E005
177 Wear_Leveling_Count     0x0013   099   099   005    Pre-fail  Always       -       11

Any idea how to read Wear_Leveling_Count?

Some values are at the minimum, some are at the maximum.

If consider "laptop" Samsung SSD 850 EVO 500GB, it is 0 and probably will go to 100, then will fail.

If consider first "server" 256 GB, SAMSUNG MZ7TE256HMHP-00000, it is already at the maximum? Will it go down to zero?

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up vote 7 down vote accepted

Kingston describe this SMART attribute as follows:

Number of erase/program cycles per block on average. This attribute is intended to be an indicator of imminent wear-out. Normalized Equation: 100 – ( 100 * Average Erase Count / NAND max rated number of erase cycles)

Ignore the Raw Data in these instances (They can be manipulated by manufacturers to work in different ways), and look at the Current Value column.

This source from Anandtech gives us a good indication of how to use this figure:

The Wear Leveling Count (WLC) SMART value gives us all the data we need. The current value stands for the remaining endurance of the drive in percentage, meaning that it starts from 100 and decreases linearly as the drive is written to. The raw WLC value counts the consumed P/E cycles, so if these two values are monitored while writing to the drive, sooner than later we will find the spot where the normalized value drops by one.

All of your drives are at between 95 and 100, and will eventually drop to 0. This is an estimation of how many write, erase, rewrite etc. cycles each block can go through before failing, and at the moment, one of your drives is estimated to have used 5% of it's current expected life span. Again, the key word here is estimated.

Note also that your drives may use different NAND technology, hence the differences in perceived life. Some NAND technology expects blocks to last for around 1000 PE cycles each, others can be rated for as much as 30,000.

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I attached the table "header". What is "current" value? is it "VALUE" column? – Nick Feb 9 at 17:36
@Nick Yes, exactly. – Jonno Feb 9 at 17:42

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