On Thu, 13 May 2010, Steve Drake wrote:
> I have had some problems with SD card corruption on the TS-7350. The usual
> symptom was that the SBC would not properly boot to the SD card and start my
> application program. However, I was always able to reimage the SD card and
> get it to working condition again. So my cards were not permanently damaged,
> just the contents were corrupted. Your case sounds like the card was
> permanently damaged.
>
> In my case, I have been able to eliminate the card corruption problems by
> flushing the filesystem using the 'sync' command before powering down, and
> also running an fsck automatically on each boot to repair the filesystem in
> case any damage has occurred. I thought the journaling filesystem would make
> these measures unnecessary, but I was wrong.
No. The journalling filesystem is designed so that if the filesystem is
NOT unmounted cleanly, e.g. power fail, then there should be information on
the disk in the journal so that an fsck on power up can complete what was
interupted. So the fsck on boot is needed. The repair should be quick
even for a very large partition.
At least that's the theory - you can never design anything for all
eventualities, but ext3 file systems do seem pretty good. Of course there
is an overhead to this. For each write to a disk file there are 3 writes to
the disk, there is a write of the operation and data to the journal, then
the journal action is implemented and the real write to file is done, then
the entry is cleared from the journal. So journalling filesystems stress
flash memory more than non-journalled filesystems.
Jim
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