-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Johnny Hughes Sent: Saturday, August 04, 2007 11:21 AM To: CentOS mailing list Subject: Re: [CentOS] 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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