Samsung SSD "Wear_Leveling_Count" meaning

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.

SMART reports a PREFAILED condition for my Samsung SM951 (AHCI) 128GB, reported in Linux as SAMSUNG MZHPV128HDGM-00000 (BXW2500Q).

But in my case I think it's a firmware bug of the drive,

• because the total-bytes-written property is reported as 1.1TB while the drive has a specified Total Bytes Written (TBW) of 75TB! Which probably is on the (very) save side, because similar (MLC NAND) drives all reached a multitude of that (600TB) in a real endurance test,
• and apart from the wear_level_count warning no other prefail or oldage errors or warnings are reported,
• while the reallocated-sector-count, which according to that test is good pre-fail indicator, is still 0.

So my advise would be to examine those values for your drive/system and base your conclusions on that.

I prefer the low level utility skdump which is supplied with libatasmart, the same library that is used by Gnome Disks.

Use the following command, replacing /dev/sdc with the path to your block device:

sudo skdump /dev/sdc