4GB SanDisk microSD && FAT32 file system

Matthias Apitz guru at unixarea.de
Fri Apr 6 16:03:55 CEST 2012


Hello,

After my bad experience with the ext3, I took another 4GB microSD
(SanDisk) and used a FAT32 file system.

The FAT32 was created on some FreeBSD laptop and I copied a tree of
48444 OpenStreetMap tiles on it. I verified the tree 3 times with 

$ find . -type f -exec md5 {} \; > md5sums

and compared the resulting output of 'md5sums', two times on the laptop
where the SD was created and once more on another laptop; the files have
been identically and fine on the SD.

Then I took the SD into a FR where the /etc/fstab was prepared to mount
it read-only. Here is what is shows:

root at om-gta02 /media/card/osm # mount | fgrep card
/dev/mmcblk0p1 on /media/card type vfat (ro,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1)
root at om-gta02 /media/card/osm # df -kh /media/card
Filesystem                Size      Used Available Use% Mounted on
/dev/mmcblk0p1            3.7G      1.5G      2.2G  41% /media/card
root at om-gta02 /media/card/osm # find . -type f | wc -l
48407
root at om-gta02 /media/card/osm # find . -type f | wc -l
find: ./13/4378: Input/output error
find: ./13/4379: Input/output error
find: ./13/4380: Input/output error
find: ./13/2190: Input/output error
find: ./13/4095: Input/output error
find: ./13/4264: Input/output error
find: ./13/4268: Input/output error
find: ./10/543: Input/output error
find: ./10/541: Input/output error
find: ./10/281: Input/output error
find: ./10/489: Input/output error
48126

i.e. the first find(1) sees only 48407 file names, the second even less;

dmesg(1) shows lines like this:

[21629.815000] FAT: Filesystem panic (dev mmcblk0p1)              
[21629.815000]     fat_get_cluster: invalid cluster chain (i_pos 0)  

Then I mounted the SD back in the laptop to check it there again and
there are now as well only 48126 files and theses file are md5 identically
with its origin.

And now?

	matthias

-- 
Matthias Apitz
t +49-89-61308 351 - f +49-89-61308 399 - m +49-170-4527211
e <guru at unixarea.de> - w http://www.unixarea.de/
UNIX since V7 on PDP-11 | UNIX on mainframe since ESER 1055 (IBM /370)
UNIX on x86 since SVR4.2 UnixWare 2.1.2 | FreeBSD since 2.2.5



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