Re: Reproducible filesystem corruption in lenny

[Josh Kelley <joshkel@gmail.com>]

On Tue, Jul 28, 2009 at 10:33 AM, Sven Joachim<svenjoac@gmx.de> wrote:
> On 2009-07-28 15:42 +0200, Josh Kelley wrote:
>> Turning off has_journal or adding -o data=journal fixes the
>> immediately preceding problem.  (I haven't tested it for our cloning
>> procedure.)  However, I don't want to go back to ext2, and
>> data=journal seems to be barely documented.  (What exactly does it
>> do?)
>
> Quoting mount.8:
>
>  All  data  is committed  into  the  journal  prior to  being
>  written into the main file system.
>
> In other words, your data are written to disk twice.

Thank you.  I also found this web page explaining data=journal in more detail:
http://www.ibm.com/developerworks/linux/library/l-fs8.html#4

> I would suggest testing the flash drives with different filesystems
> under different operating systems.  Fill it up completely, re-plug the
> device, read the data back and compare to the original.
>
> There had been cases of USB memory sticks with manipulated controllers
> produced by fraudulent manufacturers.  These sticks reported a higher
> capacity than they really had.  They never reported read or write
> errors, but once you filled more than half of the reported capacity, all
> writes would go to the same sectors, producing massive data and
> filesystem corruption.  I had bought such a scam product myself, and it
> cost me many hours of grief.

Very interesting.

I tested one of the problematic drives under Windows with FAT32 and
had no problems filling the entire contents, so that doesn't seem to
be what's happening here.

Josh Kelley