[CentOS] PATA Hard Drive woes

Wed Nov 3 22:18:06 UTC 2010
Keith Roberts <keith at karsites.net>

On Wed, 3 Nov 2010, Warren Young wrote:

> To: CentOS mailing list <centos at centos.org>
> From: Warren Young <warren at etr-usa.com>
> Subject: Re: [CentOS] PATA Hard Drive woes
> On 11/3/2010 8:32 AM, Keith Roberts wrote:
>> So to prepare the disk for returning under warranty, I used
>> another HDD utility to clean the disk again
> ...
>> So I ran an Advanced r/w scan again with Hitachi DFT, and
>> the result was OK.
> A complete disk wipe brings bad sectors to the drive's attention,
> forcing it to remap them using spare sectors set aside for the purpose.
> All drives can do this, and they do it without logging the change.  You
> can't tell, from the outside, when or whether the drive has done this.
> All you can do is infer it, because a sector that once tested bad now
> tests good.
> As to why this happened only during a format, not during the previous
> disk test, it's probably because the format zeroed the disk.  That
> particular drive may have a policy to only remap sectors on write, so as
> to preserve the sector contents for potential recovery later.  (See
> below for one way this can be done.)
> It may be that your drive is now fine.
> If you put it back into service, at minimum I would set up smartd, from
> the smartmontools package.  Maybe run smartctl on it by hand daily or
> weekly, too.  If you find that errors start happening again, there is
> something continually degrading the drive's integrity, so the automatic
> sector remapping will eventually run the drive out of spare sectors.
> SpinRite (http://spinrite.com/) does nondestructive sector remapping.
> At level 4 and above, it reads each sector in and then writes it back
> out to the drive.  Because remapping is silent, it's possible for it to
> appear to do nothing, yet improve data integrity by bringing dodgy
> sectors to the drive's attention.
> If a sector can't be read without error, SpinRite forces the drive to
> ignore the CRC and return the data anyway, retrying many times, then
> making a statistical guess about the most likely contents of the sector.
>  (Reading a bad sector won't necessarily give the same value each try.)
>  Then on writing the reconstructed data back out, the drive
> automatically remaps the sector, repairing it.
> You might want to combine the SMART monitoring with periodic SpinRite
> runs on the drive until you regain confidence in it.

Thanks Warren. I've read good reports about SpinRite.

I might shell out some dosh for a copy if it can 
non-destructably repair bad sectors. I heard it's worth 
running just to keep your HDD's in shape.