Re: [smartmontools-support] Which attributes can estimate number of bad blocks?

[<ro...@sp...>]

Current Pending Sector can indicate one of 3 things [on platter drives]:

* A bad sector that hasn't been reallocated yet, i.e. written to (a hard
error).
* A soft error. One or 2 sectors might indicate this problem. Every drive
I've seen so far with 8+ turned out to be a bad drive.
* The most insidious of all, a medium error. The sector can't hold it's
charge, for long. You can write to it then immediately read from it OK,
but usually in less than an hour, it goes corrupt again. You'll see that
in the same sector(s) keeps failing. This is a drive you should trash.

It sounds like you have a drive with medium error(s).

As for trashing a drive, it varies depending on who you ask, but at 5+
(raw value) reallocated, I trash. At 8+ Pending, I trash.

In regards to 187 and 197, I will retire a drive with any raw value more
than 0. But this is based more on Backblaze's published results than my
own observations. Usually I don't see those, or the drive is already
failing based on Reallocated and Pending.

> To get a quick estimate of the number of bad blocks that have already been
> detected, I add the raw values of attributes 5 (Reallocated_Sector_Ct) and
> 197 (Current_Pending_Sector).
>
> Should I also add the raw values of attributes 187 (Reported_Uncorrect)
> and 198 (Offline_Uncorrectable)?  Or are these redundant, already included
> in attributes 5 and 197?
>
> Are there others that I should add?
>
> Of course this estimate isn't as reliable as ... well actually, other
> methods of testing aren't particularly reliable either[*].  Anyway the
> reason for getting a quick estimate is that if we know quickly that a
> drive belongs on the scrap heap, it saves time.
>
> [* I have a drive with particularly bad firmware.  Reading the entire
> drive causes Current_Pending_Sector to increase.  Writing the bad sectors
> doesn't cause Reallocated_Sector_Ct to increase but does cause
> Current_Pending_Sector to go down to 0.  I guess the drive thinks that a
> write operation fixed the sector so the sector doesn't need reallocation,
> but the next attempt to read shows that the sector didn't get fixed.  If
> the drive were in warranty, I might not have it any more :-) ]
>
>
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