Subject: Re: [CentOS] Errors on an SSD drive



Robert Nichols wrote:
> On 08/11/2017 12:16 PM, Chris Murphy wrote:
>> On Fri, Aug 11, 2017 at 7:53 AM, Robert Nichols
>> <[email protected]> wrote:
>>> On 08/10/2017 11:06 AM, Chris Murphy wrote:
>>>>
>>>> On Thu, Aug 10, 2017, 6:48 AM Robert Moskowitz <[email protected]>
>>>> wrote:
>>>>> On 08/09/2017 10:46 AM, Chris Murphy wrote:
>>>>>>
>>>>>> If it's a bad sector problem, you'd write to sector 17066160 and see
>>>>>> if the drive complies or spits back a write error. It looks like a bad
>>>>>> sector in that the same LBA is reported each time but I've only ever
>>>>>> seen this with both a read error and a UNC error. So I'm not sure
>>>>>> it's a bad sector.
<snip>
>>>> That'll read that sector and display hex and ascii. If you recognize
>>>> the
>>>> contents, it's probably user data. Otherwise, it's file system
>>>> metadata or
>>>> a system binary.
>>>>
>>>> If you get nothing but an I/O error, then it's lost so it doesn't
>>>> matter what it is, you can definitely overwrite it.
>>>>
>>>> dd if=/dev/zero of=/dev/sda seek=17066160 count=1
>>>
>>>
>>> You really don't want to do that without first finding out what file is
>>> using that block. You will convert a detected I/O error into silent
>>> corruption ofthat file, and that is a much worse situation.
>>
>> Yeah he'd want to do an fsck -f ...

and see if repairs are made, and also

<snip>
> fsck checks filesystem metadata, not the content of files. It is not going
> to detect that a file has had 512 bytes replaced by zeros. If the file
> is a non-configuration file installed from an RPM, then "rpm -Va" should
> flag it.
>
> LVM certainly makes the procedure harder. Figuring out what filesystem
> block corresponds to that LBA is still possible, but you have to examine
> the LV layout in /etc/lvm/backup/ and learn more than you probably wanted
> to know about LVM.

I posted a link yesterday - let me know if you want me to repost it - to
someone's web page who REALLY knows about filesystems and sectors, and how
to identify the file that a bad sector is part of.

And it works. I haven't needed it in a few years, but I have followed his
directions, and identified the file on the bad sector.

mark

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