[maemo-users] Missing space on MMC2

From: Eero Tamminen eero.tamminen at nokia.com
Date: Fri Jun 27 16:58:47 EEST 2008

ext Marius Gedminas wrote:
>> Some reasons why FAT may corrupt:
>> - User disconnects the USB cable without "safely unmount"
>>    (similarly to re-inserting the memory card card, re-connecting
>>    the cable doesn't help, device and desktop OSes forget the changes
>>    once you disconnect the storage)
> (1) I almost never use USB for transferring data.
> (2) When I do, I always eject the card.
> (3) You can't access the internal card over USB when you've got an
>     active swap partition.
>> - Device HW watchdog (not the SW one) rebooting the device
> This may have happened, but how exactly can a HW watchdog reboot
> scribble random data all over the partition table and/or root directory?
> I'd understand if the FAT weren't completely updated and I'd get
> cross-linked files or missing free space, but complete garbate in the
> root dir?
>> Are you sure neither of these have happened?
> Watchdog resets have happened occasionally.  And I usually notice FS
> corruption after one of those.
> Still, that doesn't explain the other experiments I did earlier.  I
> created a 1.7 GB partition (to be really really sure I'm not
> accidentally trying to make the filesystem larger than the device),
> formatted it as VFAT and created a single large empty file (dd
> if=/dev/zero of=/media/mmc2/bigfile), and that caused vfat errors in
> dmesg and, at least once, caused the *partition table* to get
> overwritten with zeroes.  See this (short) thread:
> http://lists.maemo.org/pipermail/maemo-users/2008-March/020492.html

What if you use the whole card like Windows usually formats them
i.e. whole card is a single partition without any partition table?

Does that change anything?

>> If you're sure, is an external card more reliable?
> Yes.  I haven't ever seen FS corruption on the external card, and I
> hadn't seen FS corruption on either of the two cards in my old N800.

	- Eero

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