Yesterday i suffered from several reboots and hangups due to my
adventure with the buggy kernel-cpufreq on a core i5-750.
So i had the (unwanted) opportunity to see what ext4 recovery is like.
Saying that i have to explain that i had'nt any crashes for years and can't say how ext3 would explode my harddisk or something.
My last crash was in 2003? can't remember.
Now, what happened is:

I edited a source file. ":wq" and "make".
Unwanted sudden reboot (see above).
After reboot, that source file was empty (0 bytes). gone.

Next example, building a new kernel with menuconfig.
Saved my /root/kernelconfig, saved .config, exited menuconfig. "make". unwanted reboot, see above.
After reboot, my /root/kernelconfig is empty (0 bytes), gone.

I had expected that unsynced files are just not changed after a crash,
or, in the best case, recovered by a journal commit.
I didn't expected them to be nullified.
This seems worse than a fs corruption, because i don't notice
what happened to unsynced files now.
Is that supposed to be? What do i miss?

Thanks

What level of e2fsprogs ?.
There have been warnings about this for ages - Linus went ballistic when ext4 was merged. See lkml.

Holy cow.
I was reading about that in march or something, with
no great interest though because i was a happy user of ext3.
Thought that was long fixed.
Now i have read a bit more into that topic...this evening i reinstall
to ext3. Blaming app developers for fs behaviour is just
hilarious.
And i even don't use KDE or Gnome or something, just edited
one of my precious sources and its now gone. If my changes were
lost due to a system crash...ok, no problem. But the whole file was
nullified, even if this file was long present, not only created
and never hit the disk like mr. tso stated.
Honestly, i can't believe this beeing in a stable kernel.
Going to reinstall everything to ext3...man that will cost me hours
have to recompile lots of stuff because of changing ARCH.
Guess what? Most people (like me before) just don't care and don't realize,
because they don't experience system crashes.
Some day, big wakeup.

I remember my frustration when I first tried XFS and lost my X server config file. Actually this is the "normal" behavior of all journaling FS. Using ext4 with 2.6.29 is dangerous. You have to upgrade to at least 2.6.30.

http://lwn.net/Articles/326708/

quote:
ext4: Automatically allocate delay allocated blocks on close
ext4: Automatically allocate delay allocated blocks on rename
end quote.

Good luck.