> -----Original Message-----
> From: centos-bounces@xxxxxxxxxx
> [mailto:centos-bounces@xxxxxxxxxx] On Behalf Of Johnny Hughes
> Sent: Saturday, August 04, 2007 11:21 AM
> To: CentOS mailing list
> Subject: Re: Data corruption on external hard disk
>
> Niki Kovacs wrote:
> > Daniel de Kok a écrit :
> >> On Sat, 2007-08-04 at 07:09 +0200, Niki Kovacs wrote:
> >>> [kikinovak@buzz:/media/disk/Films] $ ls -l
> >>> total 692996
> >>> -rw-r----- 1 678756852 34537972 148381783526817280 avr
> 28 01:01 Cinema
> >>> drwxr-xr-x 3 kikinovak kikinovak 4096 mai
> 9 10:07 Anime
> >>> drwxrwxrwx 4 kikinovak kikinovak 4096 mai
> 10 12:25 Series
> >>>
> >>> Notice that the file size is something like petabytes :oD
> >>>
> >>> Is there any way to repair this obviously corrupt data?
> >>
> >> Looks like a broken inode (or incorrect directory entry).
> I'd make a
> >> backup image of the disk first (if that works without
> serious errors)
> >> with dd. After that, run a badblocks check, and a fsck.
> >>
> > Argh. Looks like a complete data loss. Well, not complete.
> Fortunately I
> > had most of it on another PC. I just lost all my films. (Gasp! David
> > Lynch gone, Hitchcock gone, Cronenberg gone...)
> >
> > Now I reformatted the HD with ext2, and badblocks is
> currently chugging
> > away for the next few hours probably.
> >
> > How do broken inodes happen? I'm a bit reluctant - for
> obvious reasons -
> > to entrust data to that disk again. Can it be that
> overheating creates
> > read/write errors, without actually corrupting the disk?
>
> Normally, unplugging external drives without unmounting them is the
> culprit on an external USB device. Also, just powering off the drive
> without unmount it if it is an externally powered drive. On
> internally
> mounted drives, usually turning off the system without
> shutting it down,
> loss of a power supply and / or loss of power to a live system.
>
> Sometimes a bad driver can cause problems for certain devices.
>
> I would use an ext3 file system as it has a journal ... and
> journals can
> recover data from the journal.
I would mount all USB drives with the 'sync' or 'dirsync' option,
if they auto-mount via Gnome or KDE then make sure which ever
config file stores the default mount options for auto-mount it
includes the 'sync' or 'dirsync' option for USB devices.
The 'sync' makes sure all io is done synchronously, the 'dirsync'
makes sure that only directory io is done synchronously which
should provide more performance than 'sync', but with less
integrity assurance.
If you need the performance you can umount the auto-mount and
then re-mount it manually without the 'sync' or 'dirsync' options.
Using a file-system that is less prone to corruption (simpler) can
also help, that is why most USB storage devices ship with FAT, that
and that FAT partitions are pretty much universally compatible.
-Ross
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