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. Regards, Keith