SSD Wear Out Calc?

Not sure if this is the best forum, but I will give it a try:

I have two 2TB Samsung 860 Pro SSDs here. Both show appr. the same SMART status:

Code:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  5 Reallocated_Sector_Ct   0x0033   100   100   010    Pre-fail  Always       -       0
  9 Power_On_Hours          0x0032   099   099   000    Old_age   Always       -       2540
 12 Power_Cycle_Count       0x0032   099   099   000    Old_age   Always       -       56
177 Wear_Leveling_Count     0x0013   099   099   000    Pre-fail  Always       -       3
179 Used_Rsvd_Blk_Cnt_Tot   0x0013   100   100   010    Pre-fail  Always       -       0
181 Program_Fail_Cnt_Total  0x0032   100   100   010    Old_age   Always       -       0
182 Erase_Fail_Count_Total  0x0032   100   100   010    Old_age   Always       -       0
183 Runtime_Bad_Block       0x0013   100   100   010    Pre-fail  Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0032   073   069   000    Old_age   Always       -       27
195 Hardware_ECC_Recovered  0x001a   200   200   000    Old_age   Always       -       0
199 UDMA_CRC_Error_Count    0x003e   100   100   000    Old_age   Always       -       0
235 Unknown_Attribute       0x0012   099   099   000    Old_age   Always       -       47
241 Total_LBAs_Written      0x0032   099   099   000    Old_age   Always       -       8775779277

Total LBAs written indicates (assuming a block size of 512 bytes) appr. 4 TB written. (This actually does make sense, because there is another mirror of two 2TB Kingston SSDs in the same striped mirrored vdev (i.e. "RAID 10"), and they also have appr. 4 TB written). I.e. I am looking at 2 drive writes in total. Why do two drive writes amount to 1% wear out (as per Proxmox), if these are 0.6 DWPD drives (with 5 years limited warranty)?
Or, looking at TBW, as per the Samsung website, these drives have 5 years warranty up to 2400 TB TBW. 4 TB is not even close to 1% of 2400 TB.

I'm pretty sure my thinking is wrong, but where?

Thanks!
 
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goseph

Active Member
Dec 4, 2014
34
1
28
I don't understand either. Can someone please explain?
In the example above it seems that the wear level is counted as this: 100-97=3%.
But Value it shows 45. What is the value for then?
Thanks a lot!
 
Last edited:

kobuki

Well-Known Member
Dec 30, 2008
470
25
48
@ThinkAgain

There are 2 more factors to take into account. First, you seem to use ZFS where commits from the ZIL cause double writes on the pool (not always; it's complicated). The Total_LBAs_Written attribute is total host writes, not taking write amplification into account (double writes are naturally accounted for, but good to keep in mind). WA directly contributes to wear. This latter one can shift your wear to around 1%.
 
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