Re: Need help to recover root filesystem after a power supply issue

Carlos E. R.
2019-07-11T02:47:47Z

[-- Attachment #1.1: Type: text/plain, Size: 1382 bytes --]

On 11/07/2019 01.43, Andrey Zhunev wrote:
>
> Ok, the ddrescue finished copying whatever it was able to recover.
> There were many unreadable sectors near the end of the drive.
> In total, there were over 170 pending sectors reported by SMART.
>
> I then ran the following commands:
>
> # smartctl -l scterc,900,100 /dev/sda
> # echo 180 > /sys/block/sda/device/timeout
>
> But this didn't help at all. The unreadable sectors still remained
> unreadable.
>
> So I wiped them with hdparm:
> # hdparm --yes-i-know-what-i-am-doing --write-sector <sector_number> /dev/sda

This has always eluded me. How did you know the sector numbers?

At this point, I typically take the brutal approach of overwriting the
entire partition (or disk) with zeroes using dd, which works as a
destructive write test ;-)

Previous to that, I attempt to create an image with ddrescue, of course.

>
> I then re-read all these sectors, and they were all read correctly.
>
> The number of pending sectors reported by SMART dropped down to 7.
> Interestingly, there are still NO reallocated sectors reported.

I suspect that the figure SMART reports only starts to rise after some
unknown amount of sectors have been remapped, so when the numbers
actually appear there, it is serious.

--
Cheers / Saludos,

Carlos E. R.
(from 15.0 x86_64 at Telcontar)

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 195 bytes --]