[maemo-users] Missing space on MMC2

From: Eero Tamminen eero.tamminen at nokia.com
Date: Fri Jun 6 17:38:40 EEST 2008

ext Marius Gedminas wrote:
> On Fri, Jun 06, 2008 at 08:18:09AM -0400, Torsten Hoefler wrote:
>> On Fri, Jun 06, 2008 at 02:24:07PM +0300, Marius Gedminas wrote:
>>> My N810 completely trashes the contents of the internal 2gb "memory
>>> card" every couple of weeks or so.  I don't trust it *at all* any more.
>> did you try to reformat?
> That's what I do: reformat the card with the File Manager on the N810,
> create a new swap file, then don't touch the card.  Later I will notice
> that after a reboot my card is showing complete garbage:
> http://mg.pov.lt/n810-fs-corruption.png
> This has happened three or four times since I got my N810.
> Initially I also had the problem with the FAT partition being a bit
> larger than the device, but reformatting it with the file manager also
> recreates the partition table, and it does that correctly.
> Then I used the internal card to keep my valuable data.  Once I started
> getting filesystem errors, rebooted and discovered that the partition
> table was overwritten by the contents of a text file.  Since then I no
> longer keep valuable data on the card.

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)
- Device HW watchdog (not the SW one) rebooting the device

Are you sure neither of these have happened?

If you're sure, is an external card more reliable?

>> I'm kind of worried to do this because another
>> filesystem might lower the lifetime of the flash-stuff by exhibiting
>> different write patterns (and since it's soldered in, I don't want to
>> destroy it faster than necessary). I'm actually even wondering if Nokia
>> changed something in the vfat implementation or if this is standard vfat
>> with the superblock in the first device blocks (seems to be very bad for
>> flash-based memory).
> I believe there's some balancing going on under the hood.  You use JFFS2
> on a MTD device on raw flash; SD cards pretend to be a regular block
> device that does write balancing in the hardware.  I believe the N810
> has the internals of a SD card soldered on the mainboard.

	- Eero

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