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



On 08/11/2017 02:32 PM, [email protected] wrote:
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.

But, have you tried it when LVM is involved? That's an additional mapping
layer for disk addresses that is not covered in the page you linked, which
is just a partial copy of the smartmontools bad block HOWTO at
https://www.smartmontools.org/browser/trunk/www/badblockhowto.xml .
That smartmontools page does have a section that deals with LVM. I advise
not looking at that on a full stomach.

--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.

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