[maemo-users] N810 built-in flash: unreliable?

From: Marius Gedminas marius at pov.lt
Date: Sun Mar 30 13:52:10 EEST 2008
Something weird is happening to my N810's internal flash memory (the
one with the VFAT-formatted 2 gig "internal memory card", not the 256
meg jffs2 root filesystem).

It appears as if writing near the end of the device wraps around and
destroys the data at the beginning.  I can reproduce it like this:

  1. Format the memory card with File Manager
  2. Open X Terminal
  3. dd if=/dev/zero of=/media/mmc2/bigfile bs=8K
  4. Wait ~10 minutes (2 gigs at 4 megs per second).
  5. dmesg

When dd fills the partition, you'll see the following message in dmesg

  [ 1793.835937] FAT: Filesystem panic (dev mmcblk0p1)
  [ 1793.835937]     fat_get_cluster: invalid cluster chain (i_pos 122753)
  [ 1793.835937]     File system has been set read-only

It's very likely that at this point your partition table also gets
overwritten and on next boot you won't see the card until you reformat

I first discovered this after a week of usage.  I had about 850 megs on
the "card" when it was remounted read-only.  I made the mistake of
rebooting and discovered that the partition table and the FAT were both
gone.  What worries me is that I was nowhere close to filling up the 2
gig partition when it broke.

I'm now trying to see if I can find a safe partition size that I can use
without losing my data.

I initially thought this might be related to

Now I'm not sure.

Marius Gedminas
To err is human, but to really foul things up requires a computer.
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