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A week ago I make a fresh OS install on a brand new ADATA SSD and wanted to check the TBW till now. Here is what I "found" in S.M.A.R.T.:

=== START OF INFORMATION SECTION ===
Device Model:     ADATA SU800
Firmware Version: P1021A
User Capacity:    512,110,190,592 bytes [512 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
Form Factor:      2.5 inches

Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
241 Total_LBAs_Written      0x0000   100   100   000    Old_age   Offline      -       6548

Device Statistics (GP Log 0x04)
Page  Offset Size        Value Flags Description
0x01  0x018  6       429149728  ---  Logical Sectors Written

In short:

  1. Total_LBAs_Written: 6548
  2. Logical Sectors Written: 429149728

Also, /proc/diskstats for /dev/sda (field #10, "sectors written"): 923561758

One thing that I notice:

sudo dumpe2fs /dev/sda3 | grep "Filesystem created" returns Sun Apr 15 01:12:02 2018 (which is when I install the OS) and till now ~253 hours has elapsed. But Power_On_Hours in S.M.A.R.T. tells 196 hours.

And here is the output of df:

  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda1       464M  200M  236M  46% /boot
  /dev/sda3       454G   58G  373G  14% /

What I'm "sure" is that the TBW should be more than 80GB (there were some files that were temporary stored on the SSD).

So, how to check the TBW and which tool to trust?

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After some digging and Googling, finally I discover how to "read" (interpret) the S.M.A.R.T attribute 241 Total_LBAs_Written.

Usually the Total_LBAs_Written shows the number of sectors written but for that drive (ADATA SU800, which is not listed in the smartctl database) this attribute shows the number of "blocks (of 32MB)" written. On other drives the name for the attr. 241 is Host_Writes_32MiB.

So, when do the math with the number from the question: (6548*32MB)/512 = 429129728 logical sectors! A number very close to the one from the "Device Statistics" info.

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