Re: About USB hard drives and errors
On 10-04-10 03:20:44, Clive McBarton wrote:
> Paul E Condon wrote:>
> > dumpe2fs -b <device> is supposed to print the bad blocks that have
> > been marked on a device. When I run it, it prints nothing. I find
> > it hard to believe that a 500GB HD contains ZERO bad blocks.
>
> Every HD that is even remotely close to being usable will always have
> zero bad blocks when seen from outside the HD. All HDs have error
> recognition and error correction and automatic replacement of faulty
> sectors with spare ones. A HD will only show bad blocks after all of
> its remapping area is used, at which point it is far beyond being
> usable.
Not quite true. If the data in a sector was not readable, the sector
will be listed as "Pending". Pending sectors are much worse than
Reallocated sectors, as Pending sectors mean lost data (if the sector
was in actual use, which SMART does not know -- and figuring out which
file might have been affected is, umm, tedious).
I keep SMART's Offline Surface Scan enabled on my drives, to have the
best chance that any failing sectors will be noticed early while they
can still be recovered. I don't mind if there are a few Reallocated
sectors, as long as there are never any Pending sectors. I'd mind if
the number of Reallocated sectors kept increasing. Of course, I also
keep backups.
> In other words, scanning for bad blocks on a HD cannot work.
Or at least normally won't, unless Data Has Been Lost.
> You can see the internal count of the remapped sectors with SMART, as
> others have already pointed out here.
Agree. Use smartctl.
--
____________________________________________________________________
TonyN.:' <mailto:tonynelson@georgeanelson.com>
' <http://www.georgeanelson.com/>
Reply to: