[smartmontools-support] Extended test doesn't catch CurrentPendingSector and OfflineUncorrectableSector errors

Christian Franke Christian.Franke at t-online.de
Sun Jul 11 18:27:47 CEST 2021

Claudio Kuenzler wrote:
>     With "smartctl -a /dev/mydevice", I can only see this information:
>     ==========================
>     197 Current_Pending_Sector  0x0032   200   200   000    Old_age  
>     Always       -       1
>     198 Offline_Uncorrectable   0x0030   200   200   000  Old_age  
>     Offline      -       6
>     ==========================
>     Is there any way to know which exact sectors are affected?
> Not with smartmontools, to my current knowledge.

Some recent drives support the "Pending Defects log". Try 'smartctl -l 
defects'. This is included in 'smartctl -x' but not in '-a'.

> But you could use "dd" or some other disk tools/commands. dd should 
> output when a read error occurs and should also print the sector(s). 
> Look at the manpage and use "noerror".

After such a read scan, some of the bad LBAs should appear in the "SMART 
(Extended Comprehensive) Error Log."
Note: Use 'smartctl -x' because '-a' only prints legacy SMART logs which 
only support 28-bit LBAs.

I often use GNU ddrescue (https://www.gnu.org/software/ddrescue/) for 
read scans. It writes a map file of good/bad/non-tried byte ranges. This 
allows to interrupt the scan at any time and resume it later. There is 
also an option to limit the read rate.
See the Bad Blocks HOWTO for a real world use case:

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