[CentOS] OT - Offline uncorrectable sectors

nate centos at linuxpowered.net
Fri Aug 22 16:26:25 UTC 2008


Lorenzo Quatrini wrote:

> For what I understand Offline uncorrectable means that the sector would be
> relocated the next time it is accessed for writing... so it is on a "wait
> for
> relocation" status.
> I don't know of any other way to force this relocation other tha actually
> writing over the sector (a simple read doesn't trigger the relocation)...

Not sure myself but the manufacturer's testing tools have
non destructive ways of detecting and re-mapping bad sectors.
Of course a downside to the manufacturer's tools is they often
only support a limited number of disk controllers.

It's probably been since the IBM Deathstar 75GXP that I last recall
having drives with bad sectors on them but typically at least at that
time, when the OS encountered a bad sector it didn't handle it too
gracefully, often times had to reboot the system. Perhaps the linux
kernel is more robust for those things these days (I had roughly 75%
of my 75GXP drives fail - more than 30).

Interesting that the man page for e2fsck in RHEL 4 doesn't describe
the -c option, but the man page for it in RHEL 3 does, not sure if
that is significant(RHEL4 man page mentions the option, but no
clear description of what it does). Haven't checked RHEL/CentOS 5.

from RHEL 3 manpage:
       -c     This option causes e2fsck to run  the  badblocks(8)
              program  to find  any blocks which are bad on the
              filesystem, and then marks them as bad by adding
              them to the  bad  block  inode.   If  this option
              is specified twice, then the bad block scan will
              be done using a non-destructive read-write test.

So if you haven't heard of it already, try e2fsck -c <device> ?
I recall using this off and on about 10 years ago but found the
manufacturer's tools to be more accurate.

> And yes, I know that a disk with bad blocks isn't reliable, but you
> remember?
> I'm too lazy to send my home disks back to the manufacturer ;)

Ahh ok, I see...just keep in mind that it's quite possible the
bad sector count will continue to mount as time goes on..

good luck ..


nate



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