Re: [libreoffice-users] Re: File corruption on OSX and LO 4252

Owen Genat wrote:
> Alex Thurgood wrote
> > ... file corruption when writing to an external disk drive. ... I have an
> > external FAT formatted LaCie hard drive to store my files on. ... I was
> > working from a USB external hard disk.

First question which occurs to me - Have you had problems with other 
drives, or only this one? It could be that the disk is failing, so it 
would be a good idea to back it up ASAP (if you don't already) just in 
case. Maybe even stop using that disk until you've tracked down the 
problem - it might stop happening with a different disk (pointing to a 
faulty disk) or it might turn out to be something else, but either way 
it'd be better to be safe! As they say, there are two types of disk - 
those which have failed, and those which will fail ;o)

> I would first try to reproduce the error without a USB external storage
> device being a factor. I cannot recommend working directly from a USB
> device. Ever. The risk of failure (in all contexts) seems to go up
> considerably when doing so and I myself have suffered from this (although
> not with LO). Not an answer I know, and you have my full sympathy and
> respect Alex, just a possible avenue for further testing.

To add to that, I've found using USB disks through a hub to be rather 
unreliable at least on the one Windows laptop I regularly use with a 
hub. It may just be my hardware or some combination of things in my 
setup, but they'll unexpectedly disconnect (and sometimes reconnect 
almost immediately), particularly while transferring large amounts of 
data (e.g. while backing up onto a USB disk). Connecting the disk 
directly to a USB port on the laptop, without the hub, is usually fine. 
I've never tracked down whether it's the laptop hardware, hub, drivers 
(either for host controller or hub) or something else, but have 
experienced this with a couple of different hubs, several different 
disks and even my scanner sometimes plays up through the hub while being 
rock solid on a direct port. Not saying it's necessarily the problem 
here, but something like that happening at the wrong moment during a 
write could corrupt a file.

> I am not discounting an LO problem as your description sounds similar to
> this bug: https://bugs.freedesktop.org/show_bug.cgi?id=78260 The example
> file does open in Writer (displays garbage),

If the file is corrupted and Writer can't work out the format, it 
interprets as plain text. The garbage seen is the raw data from the 
file, seemingly with hashes for non-printable characters. In the case of 
the file on that bug report, it looks like there is some other garbage 
(possibly fragment of a different file) at the beginning (the first "PK" 
is where the file should start), and data is missing from the end of the 
file. Looks a crash (or disk disconnect or failure) in the middle of 
writing the file has messed up the file system entries.

> but cannot be opened by an
> archive manager.

Because it's not a valid ZIP file.

> Best wishes, Owen.

Mark.

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